Method of synchronization within an LTE/LTE-A system in unlicensed spectrum

ABSTRACT

Methods, systems, and devices are described for wireless communication. One method may include receiving, at a first base station, at least one clear channel assessment (CCA)-exempt transmission (CET) indicating timing information of at least a second base station over a shared spectrum. A timing of the first base station may be adjusted based on the received timing information of the second base station. Another method of wireless communication may include identifying a CCA slot assigned to a first base station for a frame, which may be associated with time synchronization, of a shared spectrum. A CCA may be performed at the identified CCA slot for the frame. When the CCA is successful, a first timing information of the first base station may be selectively transmitted during the frame. When the CCA is unsuccessful, a second timing information of a second base station may be listened for during the frame.

CROSS REFERENCES

The present Application for Patent claims priority to U.S. ProvisionalPatent Application No. 61/908,282 by Patel et al., entitled “Method OfSynchronization Within An LTE/LTE-A System In Unlicensed Spectrum,”filed Nov. 25, 2013, assigned to the assignee hereof, and expresslyincorporated by reference herein.

BACKGROUND

Field of Disclosure

Wireless communications networks are widely deployed to provide variouscommunication services such as voice, video, packet data, messaging,broadcast, and the like. These wireless networks may be multiple-accessnetworks capable of supporting multiple users by sharing the availablenetwork resources.

Description of Related Art

A wireless communications network may include a number of access points.The access points of a cellular network may include a number of basestations, such as NodeBs (NBs) or evolved NodeBs (eNBs). The accesspoints of a wireless local area network (WLAN) may include a number ofWLAN access points, such as WiFi nodes. Each access point may supportcommunication for a number of user equipments (UEs) and may oftencommunicate with multiple UEs at the same time. Similarly, each UE maycommunicate with a number of access points, and may sometimescommunicate with multiple access points or access points employingdifferent access technologies. An access point may communicate with a UEvia downlink and uplink. The downlink (or forward link) refers to thecommunications link from the access point to the UE, and the uplink (orreverse link) refers to the communications link from the UE to theaccess point.

As cellular networks become more congested, operators are beginning tolook at ways to increase capacity, including the use of unlicensedspectrum to transmit cellular communications. In such approaches, timingand frequency synchronization among network devices associated with thesame operator, as well as across different operators using the sameunlicensed spectrum, may be useful. Traditional methods for networksynchronization, however, may be challenging to implement in the contextof unlicensed spectrum. For example, in a listen-before-talk (LBT)access scheme for unlicensed spectrum, a base station may be scheduledto transmit data during a time period that collides with thetransmission of timing and frequency synchronization information by aneighboring device. Such collisions may prevent the base station fromlistening to the timing and frequency information from the neighboringdevice.

SUMMARY

The described features generally relate to the transmission or receptionof timing information or frequency information between base stations,and to the use of such timing information or frequency information inmaking timing adjustments or frequency adjustments at a base station.The disclosed methods, systems, or devices may in some cases enable abase station to synchronize a timing or frequency with the timing orfrequency of another base station, or with a network as a whole.

Because of the utility associated with synchronizing cellular devicesdesiring to communicate over the shared spectrum, the disclosedtechniques provide for the transmission of timing information orfrequency information across different stratums of base stations. Thetiming information or frequency information may be included in or followClear Channel Assessment (CCA)-Exempt Transmissions (CETs) or CCA slots.Additionally, recursive techniques for frequency synchronization acrossdifferent stratums of base stations are provided.

A base station may adjust its timing or frequency based on timing orfrequency information received from one or multiple neighboring basestations. In some cases, base stations may be associated with timingstratums that indicate the robustness or trustworthiness of their timinginformation. Base stations associated with lower timing stratums mayhave more robust timing information (e.g., a GPS source may beassociated with the lowest timing stratum). Some of the disclosedmethods, systems, and devices take timing stratum information intoaccount when making timing or frequency adjustments to a base station'stiming or frequency. The disclosed methods, systems, and devices mayalso take into account other information, such as the line quality(ies)between a base station and its neighboring base station(s).

In some examples, a method of wireless communication includes receiving,at a first base station, at least one clear channel assessment(CCA)-exempt transmission (CET) indicating timing information of atleast a second base station over a shared spectrum, and adjusting atiming of the first base station based on the received timinginformation of at least the second base station.

In some examples, an apparatus for wireless communication includes aprocessor and memory coupled to the processor. The processor may beconfigured to receive, at a first base station, at least one clearchannel assessment (CCA)-exempt transmission (CET) indicating timinginformation of at least a second base station over a shared spectrum,and adjust a timing of the first base station based on the receivedtiming information of at least the second base station.

In some examples, a method of wireless communication includesidentifying a CCA slot assigned to a first base station for a frame of ashared spectrum, the frame may be associated with time synchronization,performing a CCA at the identified CCA slot for the frame, selectivelytransmitting a first timing information of the first base station duringthe frame when the CCA is successful, and listening for a second timinginformation of a second base station during the frame when the CCA isunsuccessful.

In some examples, an apparatus for wireless communication includes aprocessor and memory coupled to the processor. The processor may beconfigured to identify a CCA slot assigned to a first base station for aframe of a shared spectrum, the frame may be associated with timesynchronization, perform a CCA at the identified CCA slot for the frame,selectively transmit a first timing information of the first basestation during the frame when the CCA is successful, and listen for asecond timing information of a second base station during the frame whenthe CCA is unsuccessful.

Various examples of the above-described methods and apparatus mayinclude the features of, or processor configured for identifying one ofthe public land mobile network (PLMN)-specific portions associated withthe PLMN of the second base station, wherein receiving the at least oneCET comprises listening to the identified PLMN-specific portionassociated with the PLMN of the second base station for the timinginformation of the second base station. In some cases, each of the atleast one CET is received in one of a plurality of PLMN-specificportions of a CET period, each of the PLMN-specific potions assigned toone of a plurality of PLMNs, the plurality of PLMNs may include a PLMNassociated with the second base station. In some examples, the firstbase station and the second base station are members of different PLMNsassociated with different operators and the PLMNs are time synchronizedwith each other. The at least one CET may be received during a CETperiod of a plurality of periodically scheduled CET periods, and whereineach of the plurality of periodically scheduled CET periods include aplurality of PLMN-specific regions and a common transmission region. Insome cases, common transmission regions of different CET periods areassigned to different PLMNs on a rotating basis, the different PLMNs mayinclude a PLMN associated with the second base station.

In some cases, the at least one CET may include a first CET indicatingthe timing information of the second base station over the sharedspectrum and a second CET indicating timing information of a third basestation over the shared spectrum, and the first CET and the second CETmay be received concurrently. In some cases, the at least one CETfurther indicates timing information of a third base station over theshared spectrum, and various examples of the above-described methods andapparatus may include the features of, or processor configured foradjusting the timing of the first base station based on the timinginformation of the third base station.

Various examples of the above-described methods and apparatus mayinclude the features of, or processor configured for gating, based on atiming stratum of the first base station, a CCA frequency of the firstbase station for a plurality of frames associated with timingsynchronization. In some cases, a periodicity of the gating is based onthe timing stratum of the first base station.

Various examples of the above-described methods and apparatus mayinclude the features of, or processor configured for determining thatthe CCA is unsuccessful, and receiving, at the first base station, achannel usage beacon signal from the second base station for the frame.

Various examples of the above-described methods and apparatus mayinclude the features of, or processor configured for receiving thesecond timing information from the second base station during the frame,and adjusting a timing of the first base station based on the secondtiming information received from the second base station during theframe.

Various examples of the above-described methods and apparatus mayinclude the features of, or processor configured for adjusting thetiming of the first base station based on a third timing informationreceived from a third base station.

Various examples of the above-described methods and apparatus mayinclude the features of, or processor configured for determining thatthe CCA is successful, wherein the first timing information istransmitted during at least one reference signal resource element of theframe.

Various examples of the above-described methods and apparatus mayinclude the features of, or processor configured for transmitting datato at least one user equipment (UE) during the frame, wherein the datais transmitted to the UE concurrent with the transmission of the firsttiming information.

Further scope of the applicability of the described methods and deviceswill become apparent from the following detailed description, claims,and drawings. The detailed description and specific examples are givenby way of illustration only, since various changes and modificationswithin the spirit and scope of the description will become apparent tothose skilled in the art.

BRIEF DESCRIPTION OF THE DRAWINGS

A further understanding of the nature and advantages of the presentinvention may be realized by reference to the following drawings. In theappended figures, similar components or features may have the samereference label. Further, various components of the same type may bedistinguished by following the reference label by a dash and a secondlabel that distinguishes among the similar components. If only the firstreference label is used in the specification, the description isapplicable to any one of the similar components having the same firstreference label irrespective of the second reference label.

FIG. 1 shows a block diagram of a wireless communication system, inaccordance with various aspects of the present disclosure;

FIG. 2A shows a diagram that illustrates examples of deploymentscenarios for using LTE in an unlicensed spectrum, in accordance withvarious aspects of the present disclosure;

FIG. 2B shows a wireless communication system that illustrates anexample of a standalone mode for LTE/LTE-A in unlicensed spectrum, inaccordance with various aspects of the present disclosure;

FIG. 3 shows examples of an unlicensed frame/interval for a cellulardownlink in an unlicensed spectrum, in accordance with various aspectsof the present disclosure;

FIG. 4 illustrates an example of a periodic gating interval for acellular downlink in an unlicensed spectrum, in accordance with variousaspects of the present disclosure;

FIG. 5 illustrates how a contention-based protocol such as LBT may beimplemented within an S′ subframe of a gating interval, in accordancewith various aspects of the present disclosure;

FIG. 6 shows an example of CCA Exempt Transmissions (CETs), inaccordance with various aspects of the present disclosure;

FIG. 7 illustrates an example of a synchronization stratum for a deviceoperating in Timing Stratum n, in accordance with various aspects of thepresent disclosure;

FIG. 8 illustrates an example of a Super CET period, in accordance withvarious aspects of the present disclosure;

FIG. 9 illustrates an example of inter-PLMN timing adjustments, inaccordance with various aspects of the present disclosure;

FIG. 10 illustrates an example of a CET period having a plurality ofPLMN-specific regions and a common transmission region (CTR), inaccordance with various aspects of the present disclosure;

FIG. 11 illustrates an example of a CCA period having a plurality of CCAslots that are usable, at least in part, to acquire access to a sharedspectrum for the purpose of performing timing or frequencysynchronization over the shared spectrum, in accordance with variousaspects of the present disclosure;

FIG. 12 illustrates an example of a timing synchronization frame, inaccordance with various aspects of the present disclosure;

FIG. 13 shows a block diagram of an illustrative device for use inwireless communication, and more particularly CET-based timingsynchronization, in accordance with various aspects of the presentdisclosure;

FIG. 14 shows a block diagram of an illustrative device for use inwireless communication, and more particularly CET-based timingsynchronization, in accordance with various aspects of the presentdisclosure;

FIG. 15 shows a block diagram of an illustrative device for use inwireless communication, and more particularly CET-based timingsynchronization, in accordance with various aspects of the presentdisclosure;

FIG. 16 shows a block diagram of an illustrative device for use inwireless communication, and more particularly CET-based timingsynchronization, in accordance with various aspects of the presentdisclosure;

FIG. 17 shows a block diagram of an illustrative device for use inwireless communication, and more particularly CET-based timingsynchronization, in accordance with various aspects of the presentdisclosure;

FIG. 18 shows a block diagram of an illustrative device for use inwireless communication, and more particularly CET-based timingsynchronization, in accordance with various aspects of the presentdisclosure;

FIG. 19 shows a block diagram of an illustrative device for use inwireless communication, and more particularly CCA-based timingsynchronization, in accordance with various aspects of the presentdisclosure;

FIG. 20 shows a block diagram of an illustrative device for use inwireless communication, and more particularly CCA-based timingsynchronization, in accordance with various aspects of the presentdisclosure;

FIG. 21 shows a block diagram of an illustrative device for use inwireless communication, and more particularly CCA-based timingsynchronization, in accordance with various aspects of the presentdisclosure;

FIG. 22 is a message flow diagrams showing wireless communicationsbetween a first base station and a second base station, to exchangeCET-based timing information, in accordance with various aspects of thepresent disclosure;

FIG. 23 is a message flow diagrams showing wireless communicationsbetween a first base station and a second base station, to exchangeCET-based timing information, in accordance with various aspects of thepresent disclosure;

FIG. 24 is a message flow diagrams showing wireless communicationsbetween a first base station and a second base station, to exchangeCET-based timing information, in accordance with various aspects of thepresent disclosure;

FIG. 25 is a message flow diagrams showing wireless communicationsbetween a first base station and a second base station, to exchangeCET-based timing information, in accordance with various aspects of thepresent disclosure;

FIG. 26 is a message flow diagrams showing wireless communicationsbetween a first base station and a second base station, to exchangeCET-based timing information, in accordance with various aspects of thepresent disclosure;

FIG. 27 is a message flow diagrams showing wireless communicationsbetween a first base station and a second base station, to exchangeCET-based timing information, in accordance with various aspects of thepresent disclosure;

FIG. 28 is a message flow diagram illustrating wireless communicationbetween a first base station and a second base station, to exchangeCCA-based timing information, in accordance with various aspects of thepresent disclosure;

FIG. 29 is a flow chart showing an illustrative method of wirelesscommunication, and more particularly a CET-based method usable fortiming synchronization, in accordance with various aspects of thepresent disclosure;

FIG. 30 is a flow chart showing an illustrative method of wirelesscommunication, and more particularly a CET-based method usable fortiming synchronization, in accordance with various aspects of thepresent disclosure;

FIG. 31 is a flow chart showing an illustrative method of wirelesscommunication, and more particularly a CET-based method usable fortiming synchronization, in accordance with various aspects of thepresent disclosure;

FIG. 32 is a flow chart showing an illustrative method of wirelesscommunication, and more particularly a CET-based method usable fortiming synchronization, in accordance with various aspects of thepresent disclosure;

FIG. 33 is a flow chart showing an illustrative method of wirelesscommunication, and more particularly a CET-based method usable fortiming synchronization, in accordance with various aspects of thepresent disclosure;

FIG. 34 is a flow chart showing an illustrative method of wirelesscommunication, and more particularly a CCA-based method usable fortiming synchronization, in accordance with various aspects of thepresent disclosure;

FIG. 35 is a flow chart showing an illustrative method of wirelesscommunication, and more particularly a CCA-based method usable fortiming synchronization, in accordance with various aspects of thepresent disclosure;

FIG. 36 is a flow chart showing an illustrative method of wirelesscommunication, and more particularly a CCA-based method usable fortiming synchronization, in accordance with various aspects of thepresent disclosure;

FIG. 37 is a diagram of an illustrative network for which frequencysynchronization may be performed using recursive iterations of frequencyadjustments;

FIG. 38 is a diagram of an illustrative network for which frequencysynchronization may be performed using recursive iterations of frequencyadjustments, in accordance with various aspects of the presentdisclosure;

FIG. 39 is a diagram of an illustrative network for which frequencysynchronization may be performed using recursive iterations of frequencyadjustments, in accordance with various aspects of the presentdisclosure;

FIG. 40 is a diagram of an illustrative network for which frequencysynchronization may be performed using recursive iterations of frequencyadjustments, in accordance with various aspects of the presentdisclosure;

FIG. 41 is a diagram of an illustrative network for which frequencysynchronization may be performed using recursive iterations of frequencyadjustments, in accordance with various aspects of the presentdisclosure;

FIG. 42 is a diagram of an illustrative network for which frequencysynchronization may be performed using recursive iterations of frequencyadjustments, in accordance with various aspects of the presentdisclosure;

FIG. 43 is a block diagram of an illustrative device for use in wirelesscommunication in a network including a plurality of devices configuredto communicate data over an unlicensed spectrum, in accordance withvarious aspects of the present disclosure;

FIG. 44 is a block diagram of an illustrative device for use in wirelesscommunication in a network including a plurality of devices configuredto communicate data over an unlicensed spectrum, in accordance withvarious aspects of the present disclosure;

FIG. 45 is a block diagram of an illustrative device for use in wirelesscommunication in a network including a plurality of devices configuredto communicate data over an unlicensed spectrum, in accordance withvarious aspects of the present disclosure;

FIG. 46 is a flow chart of an illustrative method of wirelesscommunication in a network including a plurality of base stationsconfigured to communicate data over an unlicensed spectrum, inaccordance with various aspects of the present disclosure; and

FIG. 47 is a flow chart of an illustrative method of wirelesscommunication in a network including a plurality of base stationsconfigured to communicate data over an unlicensed spectrum, inaccordance with various aspects of the present disclosure; and

FIG. 48 shows a block diagram illustrating a base station configured forwireless communication, in accordance with various aspects of thepresent disclosure.

DETAILED DESCRIPTION

Methods, systems, and devices are described for synchronizing basestations desiring to transmit over a shared radio frequency spectrum.Because cellular devices desiring to communicate over the sharedspectrum may need to perform timing or frequency synchronization, thedisclosed techniques provide for the transmission of timing informationor frequency information across different stratums of base stations. Thetiming information or frequency information may be included in or followClear Channel Assessment (CCA)-Exempt Transmissions (CETs) or CCA slots.Additionally, recursive techniques for frequency synchronization acrossdifferent stratums of base stations are provided.

A base station may adjust its timing or frequency based on timing orfrequency information received from one or multiple neighboring basestations. In some cases, base stations may be associated with timingstratums that indicate the robustness or trustworthiness of their timinginformation. Base stations associated with lower timing stratums mayhave more robust timing information (e.g., a GPS source may beassociated with the lowest timing stratum). Some of the disclosedmethods, systems, and devices take timing stratum information intoaccount when making timing or frequency adjustments to a base station'stiming or frequency. The disclosed methods, systems, and devices mayalso take into account other information, such as the line quality(ies)between a base station and its neighboring base station(s).

In some cases, the methods, systems, and devices described herein mayprovide operators of cellular networks (e.g., operators of Long TermEvolution (LTE) or LTE-Advanced (LTE-A) communications networks) withbetter ways to synchronize the base stations that desire to use a sharedunlicensed spectrum (e.g., a WLAN spectrum typically used for WiFicommunications).

The techniques described herein are not limited to LTE, and may also beused for various wireless communication systems such as CDMA, TDMA,FDMA, OFDMA, SC-FDMA, and other systems. The terms “system” and“network” are often used interchangeably. A CDMA system may implement aradio technology such as CDMA2000, Universal Terrestrial Radio Access(UTRA), etc. CDMA2000 covers IS-2000, IS-95, and IS-856 standards.IS-2000 Releases 0 and A are commonly referred to as CDMA2000 1×, 1×,etc. IS-856 (TIA-856) is commonly referred to as CDMA2000 1×EV-DO, HighRate Packet Data (HRPD), etc. UTRA includes Wideband CDMA (WCDMA) andother variants of CDMA. A TDMA system may implement a radio technologysuch as Global System for Mobile Communications (GSM). An OFDMA systemmay implement a radio technology such as Ultra Mobile Broadband (UMB),Evolved UTRA (E-UTRA), IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE802.20, Flash-OFDM, etc. UTRA and E-UTRA are part of Universal MobileTelecommunication System (UMTS). LTE and LTE-Advanced (LTE-A) are newreleases of UMTS that use E-UTRA. UTRA, E-UTRA, UMTS, LTE, LTE-A, andGSM are described in documents from an organization named “3rdGeneration Partnership Project” (3GPP). CDMA2000 and UMB are describedin documents from an organization named “3rd Generation PartnershipProject 2” (3GPP2). The techniques described herein may be used for thesystems and radio technologies mentioned above as well as other systemsand radio technologies. The description below, however, describes an LTEsystem for purposes of example, and LTE terminology is used in much ofthe description below, although the techniques are applicable beyond LTEapplications.

The following description provides examples, and is not limiting of thescope, applicability, or configuration set forth in the claims. Changesmay be made in the function and arrangement of elements discussedwithout departing from the spirit and scope of the disclosure. Variousexamples may omit, substitute, or add various procedures or componentsas appropriate. For instance, the methods described may be performed inan order different from that described, and various steps may be added,omitted, or combined. Also, features described with respect to certainexamples may be combined in other examples.

FIG. 1 shows a block diagram of a wireless communications system 100, inaccordance with various aspects of the present disclosure. The wirelesscommunications system 100 includes a plurality of base stations 105(e.g., eNBs, WLAN access points, or other access points), a number ofuser equipments (UEs) 115, and a core network 130. Some of the basestations 105 may communicate with the UEs 115 under the control of abase station controller (not shown), which may be part of the corenetwork 130 or certain base stations 105 in various examples. Some ofthe base stations 105 may communicate control information or user datawith the core network 130 through backhaul 132. In some examples, someof the base stations 105 may communicate, either directly or indirectly,with each other over backhaul links 134, which may be wired or wirelesscommunication links. The wireless communications system 100 may supportoperation on multiple carriers (waveform signals of differentfrequencies). Multi-carrier transmitters can transmit modulated signalssimultaneously on the multiple carriers. For example, eachcommunications link 125 may be a multi-carrier signal modulatedaccording to various radio technologies. Each modulated signal may besent on a different carrier and may carry control information (e.g.,reference signals, control channels, etc.), overhead information, data,etc.

The base stations 105 may wirelessly communicate with the UEs 115 viaone or more access point antennas. Each of the base stations 105 mayprovide communication coverage for a respective coverage area 110. Insome examples, a base station 105 may be referred to as an access point,a base transceiver station (BTS), a radio base station, a radiotransceiver, a basic service set (BSS), an extended service set (ESS), aNodeB, an evolved NodeB (eNB), a Home NodeB, a Home eNodeB, a WLANaccess point, a WiFi node or some other suitable terminology. Thecoverage area 110 for an access point may be divided into sectors makingup only a portion of the coverage area (not shown). The wirelesscommunications system 100 may include base stations 105 of differenttypes (e.g., macro, micro, or pico base stations). The base stations 105may also utilize different radio technologies, such as cellular or WLANradio access technologies. The base stations 105 may be associated withthe same or different access networks or operator deployments. Thecoverage areas of different base stations 105, including the coverageareas of the same or different types of base stations 105, utilizing thesame or different radio technologies, or belonging to the same ordifferent access networks, may overlap.

In some examples, the wireless communications system 100 may include anLTE/LTE-A communications system (or network), which LTE/LTE-Acommunications system may support one or more modes of operation ordeployment in unlicensed spectrum.

In other examples, the wireless communications system 100 may supportwireless communication using access technology different from LTE/LTE-A.In LTE/LTE-A communications systems, the term evolved NodeB or eNB maybe generally used to describe of the base stations 105.

The wireless communications system 100 may be a Heterogeneous LTE/LTE-Anetwork in which different types of eNBs provide coverage for variousgeographical regions. For example, each eNB may provide communicationcoverage for a macro cell, a pico cell, a femto cell, or other types ofcell. Small cells such as pico cells, femto cells, or other types ofcells may include low power nodes or LPNs. A macro cell generally coversa relatively large geographic area (e.g., several kilometers in radius)and may allow unrestricted access by UEs with service subscriptions withthe network provider. A pico cell would generally cover a relativelysmaller geographic area and may allow unrestricted access by UEs withservice subscriptions with the network provider. A femto cell would alsogenerally cover a relatively small geographic area (e.g., a home) and,in addition to unrestricted access, may also provide restricted accessby UEs having an association with the femto cell (e.g., UEs in a closedsubscriber group (CSG), UEs for users in the home, and the like). An eNBfor a macro cell may be referred to as a macro eNB. An eNB for a picocell may be referred to as a pico eNB. And, an eNB for a femto cell maybe referred to as a femto eNB or a home eNB. An eNB may support one ormultiple (e.g., two, three, four, and the like) cells.

The core network 130 may communicate with the base stations 105 via abackhaul 132 (e.g., S1 application protocol, etc.). The base stations105 may also communicate with one another, e.g., directly or indirectlyvia backhaul links 134 (e.g., X2 application protocol, etc.) or viabackhaul 132 (e.g., through core network 130). The wirelesscommunications system 100 may support synchronous or asynchronousoperation. For synchronous operation, the base stations may have similarframe or gating timing, and transmissions from different base stationsmay be approximately aligned in time. For asynchronous operation, thebase stations may have different frame or gating timing, andtransmissions from different base stations may not be aligned in time.The techniques described herein may be used for either synchronous orasynchronous operations.

The UEs 115 may be dispersed throughout the wireless communicationssystem 100, and each UE 115 may be stationary or mobile. A UE 115 mayalso be referred to by those skilled in the art as a mobile device, amobile station, a subscriber station, a mobile unit, a subscriber unit,a wireless unit, a remote unit, a wireless device, a wirelesscommunication device, a remote device, a mobile subscriber station, anaccess terminal, a mobile terminal, a wireless terminal, a remoteterminal, a handset, a user agent, a mobile client, a client, or someother suitable terminology. A UE 115 may be a cellular phone, a personaldigital assistant (PDA), a wireless modem, a wireless communicationdevice, a handheld device, a tablet computer, a laptop computer, acordless phone, a wearable item such as a watch or glasses, a wirelesslocal loop (WLL) station, or the like. A UE 115 may be able tocommunicate with macro eNBs, pico eNBs, femto eNBs, relays, and thelike. A UE 115 may also be able to communicate over different accessnetworks, such as cellular or other WWAN access networks, or WLAN accessnetworks.

The communications links 125 shown in wireless communications system 100may include uplinks for carrying uplink (UL) transmissions (e.g., from aUE 115 to a base station 105) or downlinks for carrying downlink (DL)transmissions (e.g., from a base station 105 to a UE 115). The ULtransmissions may also be called reverse link transmissions, while theDL transmissions may also be called forward link transmissions. Thedownlink transmissions may be made using a licensed spectrum, anunlicensed spectrum, or both. Similarly, the uplink transmissions may bemade using a licensed spectrum, an unlicensed spectrum, or both.

In some examples of the wireless communications system 100, variousdeployment scenarios for LTE/LTE-A in unlicensed spectrum may besupported, including a supplemental downlink mode in which LTE downlinkcapacity in a licensed spectrum may be offloaded to an unlicensedspectrum, a carrier aggregation mode in which both LTE downlink anduplink capacity may be offloaded from a licensed spectrum to anunlicensed spectrum, and a standalone mode in which LTE downlink anduplink communications between a base station (e.g., eNB) and a UE maytake place in an unlicensed spectrum. Base stations 105 (e.g., eNBs) aswell as UEs 115 may support one or more of these or similar modes ofoperation. OFDMA communications signals may be used in thecommunications links 125 for LTE downlink transmissions in an unlicensedor a licensed spectrum, while SC-FDMA communications signals may be usedin the communications links 125 for LTE uplink transmissions in anunlicensed or a licensed spectrum.

FIG. 2A shows a diagram that illustrates examples of deploymentscenarios for using LTE in an unlicensed spectrum, in accordance withvarious aspects of the present disclosure. In one example, FIG. 2Aillustrates a wireless communications system 200 illustrating examplesof a supplemental downlink mode and a carrier aggregation mode for anLTE network that supports deployment in unlicensed spectrum. Thewireless communications system 200 may be an example of portions of thewireless communications system 100 of FIG. 1. Moreover, the base station205 may be an example of the base stations 105 of FIG. 1, while the UEs215, 215-a, and 215-b may be examples of the UEs 115 of FIG. 1.

In the example of a supplemental downlink mode in the wirelesscommunications system 200, the base station 205 may transmit OFDMAcommunications signals to a UE 215 using a downlink 220. The downlink220 may be associated with a frequency F1 in an unlicensed spectrum. Thebase station 205 may transmit OFDMA communications signals to the sameUE 215 using a bidirectional link 225 and may receive SC-FDMAcommunications signals from that UE 215 using the bidirectional link225. The bidirectional link 225 may be associated with a frequency F4 ina licensed spectrum. The downlink 220 in the unlicensed spectrum and thebidirectional link 225 in the licensed spectrum may operateconcurrently. The downlink 220 may provide a downlink capacity offloadfor the base station 205. In some examples, the downlink 220 may be usedfor unicast services (e.g., addressed to one UE) services or formulticast services (e.g., addressed to several UEs). This scenario mayoccur with any service provider (e.g., traditional mobile networkoperator (MNO)) that uses a licensed spectrum and needs to relieve someof the traffic or signaling congestion.

In one example of a carrier aggregation mode in the wirelesscommunications system 200, the base station 205 may transmit OFDMAcommunications signals to a UE 215-a using a bidirectional link 230 andmay receive SC-FDMA communications signals from the same UE 215-a usingthe bidirectional link 230. The bidirectional link 230 may be associatedwith the frequency F1 in the unlicensed spectrum. The base station 205may also transmit OFDMA communications signals to the same UE 215-ausing a bidirectional link 235 and may receive SC-FDMA communicationssignals from the same UE 215-a using the bidirectional link 235. Thebidirectional link 235 may be associated with a frequency F2 in alicensed spectrum. The bidirectional link 230 may provide a downlink anduplink capacity offload for the base station 205. Like the supplementaldownlink described above, this scenario may occur with any serviceprovider (e.g., MNO) that uses a licensed spectrum and needs to relievesome of the traffic or signaling congestion.

In another example of a carrier aggregation mode in the wirelesscommunications system 200, the base station 205 may transmit OFDMAcommunications signals to a UE 215-b using a bidirectional link 240 andmay receive SC-FDMA communications signals from the same UE 215-b usingthe bidirectional link 240. The bidirectional link 240 may be associatedwith a frequency F3 in an unlicensed spectrum. The base station 205 mayalso transmit OFDMA communications signals to the same UE 215-b using abidirectional link 245 and may receive SC-FDMA communications signalsfrom the same UE 215-b using the bidirectional link 245. Thebidirectional link 245 may be associated with the frequency F2 in thelicensed spectrum. The bidirectional link 240 may provide a downlink anduplink capacity offload for the base station 205. This example and thoseprovided above are presented for illustrative purposes and there may beother similar modes of operation or deployment scenarios that combineLTE/LTE-A in licensed and unlicensed spectrum for capacity offload.

As described above, the typical service provider that may benefit fromthe capacity offload offered by using LTE/LTE-A in unlicensed spectrumis a traditional MNO with LTE spectrum. For these service providers, anoperational configuration may include a bootstrapped mode (e.g.,supplemental downlink, carrier aggregation) that uses the LTE primarycomponent carrier (PCC) on the licensed spectrum and a secondarycomponent carrier (SCC) on the unlicensed spectrum.

In the carrier aggregation mode, data and control may generally becommunicated in the licensed spectrum (e.g., bidirectional links 225,235, and 245) while data may generally be communicated in the unlicensedspectrum (e.g., bidirectional links 230 and 240). The carrieraggregation mechanisms supported when using unlicensed spectrum may fallunder a hybrid frequency division duplexing-time division duplexing(FDD-TDD) carrier aggregation or a TDD-TDD carrier aggregation withdifferent symmetry across component carriers.

FIG. 2B shows a wireless communication system 250 that illustrates anexample of a standalone mode for LTE/LTE-A in unlicensed spectrum, inaccordance with various aspects of the present disclosure. The wirelesscommunication system 250 may be an example of portions of the wirelesscommunications system 100 of FIG. 1 or 200 of FIG. 2A. Moreover, thebase station 205 may be an example of the base stations 105 or 205described with reference to FIG. 1 or 2A, while the UE 215-c may be anexample of the UEs 115 or 215 of FIG. 1 or 2A.

In the example of a standalone mode in the wireless communication system250, the base station 205 may transmit OFDMA communications signals tothe UE 215-c using a bidirectional link 255 and may receive SC-FDMAcommunications signals from the UE 215-c using the bidirectional link255. The bidirectional link 255 may be associated with the frequency F3in an unlicensed spectrum described above with reference to FIG. 2A. Thestandalone mode may be used in non-traditional wireless accessscenarios, such as in-stadium access (e.g., unicast, multicast). Thetypical service provider for this mode of operation may be a stadiumowner, cable company, event host, hotel, enterprise, or largecorporation that does not have licensed spectrum.

In some examples, a transmitting device such as a base station 105, 205described with reference to FIG. 1, 2A, or 2B, or a UE 115 or 215described with reference to FIG. 1, 2A, or 2B, may use a gating intervalto gain access to a channel of the shared spectrum (e.g., to a physicalchannel of the licensed or unlicensed spectrum). The gating interval maydefine the application of a contention-based protocol, such as a ListenBefore Talk (LBT) protocol based on the LBT protocol specified in ETSI(EN 301 893). When using a gating interval that defines the applicationof an LBT protocol, the gating interval may indicate when a transmittingdevice needs to perform a Clear Channel Assessment (CCA). The outcome ofthe CCA may indicate to the transmitting device whether a channel of theshared unlicensed spectrum is available or in use. When the CCAindicates that the channel is available (e.g., “clear” for use), thegating interval may allow the transmitting device to use thechannel—typically for a predefined transmission interval. When the CCAindicates that the channel is not available (e.g., in use or reserved),the gating interval may prevent the transmitting device from using thechannel during the transmission interval.

In some cases, it may be useful for a transmitting device to generate agating interval on a periodic basis and synchronize at least oneboundary of the gating interval with at least one boundary of a periodicframe structure. For example, it may be useful to generate a periodicgating interval for a cellular downlink in a shared spectrum, and tosynchronize at least one boundary of the periodic gating interval withat least one boundary of a periodic frame structure (e.g., LTE/LTE-Aradio frame) associated with the cellular downlink. Examples of suchsynchronization are shown in FIG. 3.

FIG. 3 shows examples 300 of an unlicensed frame/interval 305, 315, or325 for a cellular downlink in an unlicensed spectrum, in accordancewith various aspects of the present disclosure. The unlicensedframe/interval 305, 315, or 325 may be used as a periodic gatinginterval by an eNB that supports transmissions over the unlicensedspectrum. Examples of such an eNB may include the base stations 105, 205described with reference to FIG. 1, 2A, or 2B. The unlicensedframe/interval 305, 315, or 325 may be used with the wirelesscommunications system 100, 200, or 250 described with reference to FIG.1, 2A, or 2B.

By way of example, the duration of the unlicensed frame/interval 305 isshown to be equal to (or approximately equal to) a duration of anLTE/LTE-A radio frame 310 of a periodic frame structure associated witha cellular downlink. In some examples, “approximately equal” means theduration of the unlicensed frame/interval 305 is within a cyclic prefix(CP) duration of the duration of the periodic frame structure.

At least one boundary of the unlicensed frame/interval 305 may besynchronized with at least one boundary of the periodic frame structurethat includes the LTE/LTE-A radio frames N−1 to N+1. In some cases, theunlicensed frame/interval 305 may have boundaries that are aligned withthe frame boundaries of the periodic frame structure. In other cases,the unlicensed frame/interval 305 may have boundaries that aresynchronized with, but offset from, the frame boundaries of the periodicframe structure. For example, the boundaries of the unlicensedframe/interval 305 may be aligned with subframe boundaries of theperiodic frame structure, or with subframe midpoint boundaries (e.g.,the midpoints of particular subframes) of the periodic frame structure.

In some cases, the periodic frame structure may include LTE/LTE-A radioframes N−1 to N+1. Each LTE/LTE-A radio frame 310 may have a duration often milliseconds, for example, and the unlicensed frame/interval 305 mayalso have a duration of ten milliseconds. In these cases, the boundariesof the unlicensed frame/interval 305 may be synchronized with theboundaries (e.g., frame boundaries, subframe boundaries, or subframemidpoint boundaries) of one of the LTE/LTE-A radio frames (e.g., theLTE/LTE-A radio frame (N)).

By way of example, the duration of the unlicensed frames/intervals 315and 325 are shown to be sub-multiples of (or approximate sub-multiplesof) the duration of the periodic frame structure associated with thecellular downlink. In some examples, an “approximate sub-multiple of”means the duration of the unlicensed frame/interval 315, 325 is within acyclic prefix (CP) duration of the duration of a sub-multiple of (e.g.,half or one-tenth) the periodic frame structure. For example, theunlicensed frame/interval 315 may have a duration of five millisecondsand the unlicensed frame/interval 325 may have a duration of 1 or 2milliseconds.

FIG. 4 illustrates an example 400 of a periodic gating interval 405 fora cellular downlink in an unlicensed spectrum. The periodic gatinginterval 405 may be used by a base station that supports communicationin a shared spectrum. Examples of such a base station include the basestations 105 and 205 described with reference to FIG. 1, 2A, or 2B. Theperiodic gating interval 405 may be used with the wirelesscommunications system 100, 200, or 250 of FIG. 1, 2A, and or 2B.

By way of example, the duration of the periodic gating interval 405 isshown to be equal to (or approximately equal to) the duration of aperiodic frame structure 410, 415, 420 associated with the cellulardownlink. The boundaries of the periodic gating interval 405 may besynchronized with (e.g., aligned with) the boundaries of the periodicframe structure 410, 415, 420.

The periodic frame structure 410, 415, 420 may include an LTE/LTE-Aradio frame 415 having ten subframes (e.g., SF0, SF1, . . . , SF9).Subframes SF0 through SF8 may be downlink (D) subframes 425, andsubframe SF9 may be a special (S′) subframe 430. The D subframes 425 maycollectively define a channel occupancy time of the LTE radio frame, andat least part of the S′ subframe 430 may define a channel idle time.Under the current LTE/LTE-A standards, an LTE/LTE-A radio frame may havea maximum channel occupancy time (ON time) between one and 9.5milliseconds, and a minimum channel idle time (OFF time) of five percentof the channel occupancy time (e.g., a minimum of 50 microseconds). Toensure compliance with the LTE/LTE-A standards, the periodic gatinginterval 405 may abide by these requirements of the LTE/LTE-A standardby providing a 0.5 millisecond guard period (i.e., OFF time) as part ofthe S′ subframe 430.

Because the S′ subframe 430 has a duration of one millisecond, it mayinclude one or more CCA slots 435 in which the transmitting devicescontending for a particular physical channel of an unlicensed spectrummay perform their CCAs. When a transmitting device's CCA indicates thephysical channel is available, but the device's CCA is completed beforethe end of the periodic gating interval 405, the device may transmit oneor more signals 440 to reserve the channel until the end of the periodicgating interval 405. The one or more signals 440 may in some casesinclude a Channel Usage Pilot Signal (CUPS), a Channel Usage BeaconSignal (CUBS), or a cell-specific reference signal (CRS). As used in thepresent disclosure and the appended claims, the terms “Channel UsagePilot Signal (CUPS)” and “Channel Usage Beacon Signal (CUBS)” areinterchangeable. CUPS or a CRS may be used for both channelsynchronization and channel reservation. That is, a device that performsa CCA for the channel after another device begins to transmit CUPS onthe channel may detect the energy of the CUPS and determine that thechannel is currently unavailable.

Following a transmitting device's successful completion of CCA for aphysical channel or the transmission of CUPS over a physical channel,the transmitting device may use the physical channel for up to apredetermined period of time (e.g., one LTE/LTE-A radio frame) totransmit a waveform (e.g., an LTE-based waveform 445 associated with aphysical carrier).

FIG. 5 illustrates how a contention-based protocol such as LBT may beimplemented within an S′ subframe 500 of a gating interval, such as anS′ subframe of the ten millisecond periodic gating interval 405described with reference to FIG. 4. The contention-based protocol may beused with, for example, the wireless communications system 100, 200, or250, base stations 105 or 205, or UEs 115 or 215 described withreference to FIG. 1, 2A, or 2B.

The S′ subframe 500 may have a guard period (or silent period) 505 and aCCA period 510. By way of example, each of the guard period 505 and theCCA period 510 may have a duration of 0.5 milliseconds and include sevenOFDM symbol positions 515 (labeled in FIG. 5 as Slots 1 through 7). Insome cases, a base station may select one or more of the OFDM symbolpositions 515 to perform a CCA 520 for a subsequent transmissioninterval of an unlicensed spectrum, to determine whether thetransmission interval of the unlicensed spectrum is available for atransmission during the transmission interval. In some cases, differentones of the OFDM symbol positions 515 may be pseudo-randomly identifiedor selected by a base station in different occurrences of the S′subframe 500 (i.e., in different S′ subframes used to perform CCA 520for different transmission intervals of the unlicensed spectrum). Thepseudo-random identification or selection of OFDM symbol positions maybe controlled using a hopping sequence.

The base stations of a wireless communications system may be operated bythe same or different operators. In some examples, the base stationsoperated by different operators (e.g., the base stations belonging todifferent Public Land Mobile Networks (PLMNs) may select different onesof the OFDM symbol positions 515 in a particular S′ subframe 500,thereby avoiding CCA collisions between different operators. If thepseudo-random selection mechanisms of different operators arecoordinated, OFDM symbol positions 515 may be pseudo-randomly selectedby a plurality of different operators such that the base stations of thedifferent operators each have an equal opportunity to perform CCA 520 inthe earliest OFDM symbol position (i.e., Slot 1) for certaintransmission intervals. Thus, over time, the base stations of thedifferent operators may each have an opportunity to perform CCA 520first and gain access to a transmission interval of the unlicensedspectrum regardless of the needs of eNBs of other operators. After asuccessful CCA 520, a base station may transmit CUPS to prevent otherdevices or operators from using one or more physical channels of thetransmission interval of the unlicensed spectrum.

FIG. 6 shows an example 600 of CCA Exempt Transmissions (CETs), inaccordance with various aspects of the present disclosure. As shown, anallocation of resources for CETs may be made, for example, once everyeighty milliseconds (80 ms). Each of a number of operators in theunlicensed spectrum (e.g., different PLMNs) may be provided a separatesubframe for transmitting CETs. By way of example, FIG. 6 shows adjacentCET subframes for seven different operators (e.g., operators PLMN1,PLMN2, . . . , PLMN7). Such a structure may be applicable to bothdownlink and uplink subframes.

In a wireless communications spectrum shared by cellular and WiFidevices, the WiFi devices operate in an ad hoc manner and do not providetiming or frequency references to which cellular devices may sync.Methods and devices that enable cellular devices to operate in asynchronous manner over such a network may therefore be desirable.

In the context of an LTE network, 3GPP TR 36.922 V9.1.0 (2010-07)describes a “network listening” technique for synchronizing a first HomeeNB (HeNB) to a second HeNB or an eNB. The network listening techniqueintroduces the concept of a “synchronization stratum,” which is definedas the smallest number of hops between a particular HeNB and a GPSsource (e.g., a GPS-synchronized HeNB or eNB).

FIG. 7 illustrates an example of a synchronization stratum 700 for adevice operating in Timing Stratum n. The device operating in the TimingStratum n may obtain (e.g., track) timing information from a deviceoperating in Timing Stratum n−1 and so on. A device operating in TimingStratum 2 may obtain timing information from a device operating inTiming Stratum 1. The device operating in Timing Stratum 1 may be a GPSsource or other trusted synchronization source. When devices in a lowerstratum are scheduled to transmit and receive timing information,devices in a higher stratum (e.g., a next higher stratum) may listen fortiming information transmitted by the devices of a lower stratum (e.g.,a next lower stratum). In some cases, a listening device may gate itstransmissions when listening for timing information, to mitigateinterference with its receipt of timing information.

As described in 3GPP TR 36.922, the timing information of a device maybe obtained from one or more signals transmitted by the device,including, for example, a Common Reference Signal (CRS) transmitted bythe device. The one or more signals carrying the timing information mayin some cases be transmitted in a non-MBSFN part of aMulticast-Broadcast Single-Frequency Network (MBSFN) subframe or a guardperiod of a special subframe. In some cases, information indicating acorrespondence between timing stratums and the timings of timingsynchronization signals may be provided to all network devices (e.g., inmessages defined by RAN3), such that a device's timing synchronizationsignals (e.g., CRS) may convey the timing stratum of the device.

Described below are various ways to adjust (e.g., synchronize) thetiming and frequency of cellular devices using a shared spectrum. Thedescribed timing and frequency adjustment techniques may extend certainaspects of the 3GPP TR 36.922 “network listening” technique to LTE/LTE-Anetworks operating in unlicensed spectrum. The timing adjustmenttechniques described with reference to FIGS. 8-10 are CET-based, whereasthe timing adjustment techniques described with reference to FIGS. 11and 12 are CCA-based.

FIG. 8 illustrates an example of a Super CET period 800. In contrast tothe CET period described with reference to FIG. 6, the Super CET period800 may be expanded to include, for example, the entirety of an LTEradio frame (e.g., 10 subframes, 140 OFDM symbols, and 10 milliseconds).To amortize the overhead of the Super CET period 800, the Super CETperiod 800 may be allocated, for example, once every 800 milliseconds. ASuper CET period 800 consuming one LTE radio frame (10 milliseconds)every 800 milliseconds provides an overhead rate of 1.25%. If Super CETperiods replace regular CET periods (e.g., every 10th CET period), theincrease in overhead attributable to Super CET periods may be less than1.25%.

As shown, a Super CET period 800 may include a plurality ofPLMN-specific portions 805, 810, 815, 820, 825, 830, 835. EachPLMN-specific portion may be assigned to one of a plurality of differentPLMNs (e.g., one of seven different PLMNs, noted in FIG. 8 as PLMN1,PLMN2, PLMN3, PLMN4, PLMN5, PLMN6, and PLMN7). By way of example, eachPLMN-specific portion may include 20 OFDM symbols. Each set of 20 OFDMsymbols may provide five slots (e.g., slots 840, 845, 850, 855, and 860)in which to transmit a CET corresponding to a particular PLMN. Each slotmay be four OFDM symbols long and may carry a regular CET waveform.

Devices (e.g., base stations) associated with lower timing stratums maytransmit a CET multiple times (e.g., up to five times) within onePLMN-specific portion. However (and assuming there are no more than fivetiming stratums), the devices of every stratum may be provided a slot inwhich to transmit a CET without interference from higher stratums. Forexample, the devices of Timing Stratum 1 in PLMN1 may each transmit aCET in the first four OFDM symbols of a PLMN-specific portion; thedevices of Timing Stratum 1 and Timing Stratum 2 in PLMN1 may eachtransmit a CET in the second four OFDM symbols; the devices of TimingStratums 1-3 may each transmit a CET in the third four OFDM symbols; thedevices of Timing Stratums 1-4 may each transmit a CET in the fourthfour OFDM symbols; and all devices of all timing stratums may eachtransmit a CET in the fifth four OFDM symbols.

Inter-PLMN orthogonality is maintained in the Super CET period, andevery device of a timing stratum higher than Timing Stratum 1 may havean opportunity to listen for timing information of another device, withthe other device being in a lower stratum of the same PLMN (i.e., in thesame operator deployment).

Although the Super CET period 800 shown in FIG. 8 is intended fordownlink synchronization, a similar structure may be used forUE-assisted uplink synchronization.

FIG. 9 illustrates an example 900 of inter-PLMN timing adjustments,where a device (e.g., a base station) that is a member of a PLMNassociated with one operator (e.g., a first operator) listens for timinginformation, and adjusts its timing, based on the timing information itreceives from another device, which other device may be a member of aPLMN associated with a different operator (e.g., a second operator).

As shown, and by way of example, the devices of PLMN1 may adjust theirtiming based on timing information received in one or more CETs 910 fromdevices of PLMN2; the devices of PLMN2 may adjust their timing based ontiming information received in one or more CETs 915 from devices ofPLMN3; the devices of PLMN3 may adjust their timing based on timinginformation received in one or more CETs 920 from devices of PLMN4; thedevices of PLMN4 may adjust their timing based on timing informationreceived in one or more CETs 925 from devices of PLMN5; the devices ofPLMN5 may adjust their timing based on timing information received inone or more CETs 930 from devices of PLMN6; the devices of PLMN6 mayadjust their timing based on timing information received in one or moreCETs 935 from devices of PLMN7; and the devices of PLMN7 may adjusttheir timing based on timing information received in one or more CETs905 from devices of PLMN1.

In some cases, a device may adjust its timing based on a strongestneighbor (i.e., strongest neighbor device) of another PLMN. In somecases, a different timing stratum may be present in a different PLMN asthe dominant neighbor. This may be taken advantage of, for example, byencoding the timing stratum number in a System Information Block 0(i.e., SIB0). The frequency of timing stratum number change may berestricted.

Some potential advantages of the timing adjustment technique describedwith reference to FIG. 9 are that 1) it may require relatively littleeffort to setup or manage, and 2) it may enable good reuse among PLMNs,with a guaranteed receive opportunity. Some potential disadvantages arethat it does not work in the case of a single PLMN (e.g., because thereis no other PLMN to sync to); time tracking accuracy may be questionabledue to low duty cycle (e.g., 80 milliseconds); and frequency trackingmay be questionable due to a less than three millisecond usefulobservation window.

FIG. 10 illustrates an example of a CET period 1000 having a pluralityof PLMN-specific regions 1005, 1010, 1015, 1020, 1025, 1030 and a commontransmission region (CTR) 1035. The CET period 1000 may have a structuresimilar to the CET period 699 described with reference to FIG. 6, butwith the last slot of the CET period being replaced with the CTR 1035.The CTR 1035 may be assigned to different PLMNs in different CET periodson a rotating basis. Thus, when the CET period 1000 occurs every 80milliseconds and provides PLMN-specific regions 1005, 1010, 1015, 1020,1025, 1030 for six PLMNS, a PLMN may have access to the CTR 1035 every480 milliseconds.

In some cases, the PLMN-specific regions 1005, 1010, 1015, 1020, 1025,1030 may have a time rank order, and PLMN-specific regions havingdifferent time ranks may be assigned to different PLMNs in different CETperiods. In these cases, the CTR 1035 may be assigned to different PLMNsin different CET periods based on the PLMN assignment of a PLMN-specificregion having a particular time rank. For example, the PLMN-specificregion having the highest time rank (i.e., the PLMN-specific region 1030having time rank 5 in FIG. 10) may determine the CTR assignment, suchthat the PLMN-specific region 1030 having the highest time rank and theCTR 1035 are assigned to a common PLMN.

When a PLMN has access to the CTR 1035, and in some examples, the basestations of the PLMN may transmit CETs with their respective timinginformation over a shared spectrum during the CTR 1035. CETs may beconcurrently transmitted during the CTR 1035, regardless of stratum.Each CET transmitted in the CTR 1035 may include the same MBSFN-likesynchronization signal. Base stations associated with the lowest timingstratum (e.g., GPS sync sources) may always transmit CETs during the CTR1035. Base stations associated with higher timing stratums may track theCTR 1035 to acquire timing and frequency synchronization information,and may then transmit their own CETs during the CTR 1035. Base stationsassociated with higher timing stratums may periodically gate (i.e., nottransmit) their CETs, in order to listen for timing information of otherbase stations and maintain their time and frequency synchronization.Gating activity may be evenly distributed among the higher stratumdevices of a PLMN.

When base stations of a PLMN concurrently transmit CETs in a particularCTR 1035, regardless of stratum, a base station of a higher stratum maytrack to an aggregate path delay profile of its PLMN, as measured by theCTR signal. The frequency of a base station's tracking rate may bereduced by its gating rate. Thus, for a 25% gating rate, a basestation's tracking rate may be reduced to 4*6*(80 milliseconds)=1.92seconds.

Also, when base stations of a PLMN concurrently transmit CETs in aparticular CTR 1035, regardless of stratum, there is no guarantee ofconvergence to Timing Stratum 1 timing (e.g., GPS timing), and there isa possibility of time and frequency oscillations (e.g., Base Station Asyncs to Base Station B, Base Station B syncs to Base Station C, andBase Station C syncs to Base Station A). The possibility of time andfrequency oscillations increases when operating, for example, in astandalone mode without a GPS source, where all base stations may berequired to periodically sync to their neighbors.

In some examples, the CTR 1035 may be further assigned to one of aplurality of timing stratums of the assigned PLMN on a rotating basis.Stated another way, the CTR 1035 may be assigned to differentcombinations of PLMN and timing stratum on a rotating basis. Thus, whenthe CET period occurs every 80 milliseconds and provides slots for sixPLMNS having four timing stratums, a PLMN may have access to the CTR1035 every 1.92 seconds. In these examples, a base station may adjustits timing in response to a lower stratum (or stratums), which maymitigate the possibility of synchronization loops or misconvergenceissues.

With any of the timing adjustment techniques described in FIG. 8-10, abase station may periodically gate a transmission of its own CET tocapture timing information of another base station in its own PLMN. Thegating may be performed according to a periodic gating schedule thatindicates particular CET period(s) in which the CET of the base stationshould be gated to mitigate interference with the base station's receiptof a CET of at least one other base station in its PLMN. The periodicgating schedule may have a low periodicity. Gating activity may beevenly distributed among the higher stratum devices of a PLMN.

Also with any of the timing adjustment techniques described in FIG. 8,9, or 10, a Physical Broadcast Control Channel (PBCCH) may be used toassign timing stratums to base stations.

FIG. 11 illustrates an example 1100 of a CCA period 1110 having aplurality of CCA slots 1115 (e.g., Slot 1, Slot 2, Slot 3, Slot 4, Slot5, Slot 6, and Slot 7) that are usable, at least in part, to acquireaccess to a shared spectrum for the purpose of performing timing orfrequency synchronization over the shared spectrum. The CCA period 1110may in some cases be part of a subframe (e.g., an S subframe). Thesubframe may also include a guard period 1105.

In some examples, a different timing stratum (e.g., TS1, TS2, TS3, TS4,TS5, TS6, or TS7) may be assigned to each of the CCA slots 1115.

In use, a device (e.g., a base station such as the base station 105 or205 described with reference to FIG. 1, 2A, or 2B) may perform a CCA1120 in a CCA slot 1115 to which its associated timing stratum isassigned. Thus, a device associated with timing stratum 1 (e.g., a GPSsource) would perform a CCA 1120 in Slot 1, whereas a device associatedwith timing stratum 4 would perform a CCA 1120 in Slot 4. Uponsuccessfully performing a CCA 1120, a device may transmit a signal suchas a CUBS or a CRS to reserve the frame following the CCA period 1110.The device may then transmit timing information in the reserved frame(e.g., a CRS).

In contrast to the CCA period 510 described with reference to FIG. 5,different timing stratums, instead of different PLMNs, are assigned tothe CCA slots 1115. Every device sharing a particular timing stratumtherefore performs a CCA in the CCA slot 1115 assigned to its timingstratum.

FIG. 12 illustrates an example 1200 of a timing synchronization frame1215. The timing synchronization frame 1215 has a plurality of CCA 1265slots that are usable in a cellular downlink to acquire access to ashared spectrum for the purpose of performing timing or frequencysynchronization over the shared spectrum. The timing synchronizationframe 1215 may be bounded by other types of frames 1210, 1220 and mayperiodically repeat.

The timing synchronization frame 1215 may include an LTE/LTE-A radioframe having ten subframes (e.g., SF0, SF1, . . . , SF9). Even numberedsubframes SF0, SF2, SF4, SF6, and SF8 may be downlink (D) subframes1225, subframes SF1, SF3, SF5, and SF7 may be special (S″) subframes1260, and subframe SF9 may be a special (S′) subframe 1230. The S′subframe SF9 may be used by a base station to perform a CCA 1235. TheCCA 1235 may be similar to the CCA described with reference to FIG. 4 or5. When the CCA 1235 is successful, a device performing the CCA 1235 maytransmit a signal (e.g., CUBS 1240) to reserve a subsequent transmissionperiod 1245 of the shared spectrum. The S″ subframes SF1, SF3, SF5, andSF7 may be used by a base station to perform a CCA 1265. The CCA 1265may be similar to the CCA described with reference to FIG. 11. That is,each of the CCAs 1265 shown in FIG. 12 may be associated with adifferent timing stratum. When a device successfully performs a CCA1265, the device performing the CCA 1265 may transmit a signal (e.g.,CUBS 1250) to reserve a subsequent transmission period 1255 in which thedevice may transmit timing information. Because each CCA slot enablesthe devices associated with a timing stratum to access the sharedspectrum for only a limited period of time within the timingsynchronization frame 1215, devices associated with other timingstratums may also be provided opportunities to access the sharedspectrum and transmit timing information. The synchronization frame 1215shown in FIG. 12 may provide more efficient and timely use ofsynchronization frame resources.

FIG. 13 shows a block diagram 1300 of a device 1305 for use in wirelesscommunication, in accordance with various aspects of the presentdisclosure. In some examples, the device 1305 may be an example of oneor more aspects of one of the base stations 105 or 205 described withreference to FIG. 1, 2A, or 2B. The device 1305 may also be a processor.The device 1305 may include a receiver module 1310, a timing managementmodule 1315, and a transmitter module 1320. Each of these components maybe in communication with each other.

The components of the device 1305 may, individually or collectively, beimplemented using one or more application-specific integrated circuits(ASICs) adapted to perform some or all of the applicable functions inhardware. Alternatively, the functions may be performed by one or moreother processing units (or cores), on one or more integrated circuits.In other examples, other types of integrated circuits may be used (e.g.,Structured/Platform ASICs, Field Programmable Gate Arrays (FPGAs), andother Semi-Custom ICs), which may be programmed in any manner known inthe art. The functions of each unit may also be implemented, in whole orin part, with instructions embodied in a memory, formatted to beexecuted by one or more general or application-specific processors.

In some examples, the receiver module 1310 may be or include a radiofrequency (RF) receiver, such as an RF receiver operable to receivetransmissions in a first spectrum (e.g., a licensed LTE spectrum) or asecond spectrum (e.g., a “shared spectrum” used by devices operatingunder different transmission protocols, such as an unlicensed spectrum).The receiver module 1310 may be used to receive various types of data orcontrol signals (i.e., transmissions) over one or more communicationlinks of a wireless communications system including the first and secondspectrums, such as one or more communication links of the wirelesscommunications system 100, 200, or 250 described with reference to FIG.1, 2A, or 2B.

In some examples, the transmitter module 1320 may be or include an RFtransmitter, such as an RF transmitter operable to transmit in the firstspectrum or the second spectrum. The transmitter module 1320 may be usedto transmit various types of data or control signals (i.e.,transmissions) over one or more communication links of the wirelesscommunications system including the first spectrum and the secondspectrum.

In some examples, the timing management module 1315 may receive timinginformation of at least a second device (e.g., at least a second basestation) over a shared spectrum. The timing management module 1315 mayuse the received timing information to adjust the timing of the device1305. The timing management module 1315 may also transmit timinginformation of the device 1305 to other devices (e.g., other basestations). As described below with reference to FIGS. 14-18, timinginformation may in some cases be transmitted or received during a CETperiod. Timing information may alternately (or also) be transmitted orreceived during a CCA period, as described below with reference to FIGS.19-21.

FIG. 14 shows a block diagram 1400 of a device 1405 for use in wirelesscommunication, in accordance with various aspects of the presentdisclosure. In some examples, the device 1405 may be an example of oneor more aspects of one of the base stations 105 or 205 described withreference to FIG. 1 or 2, or the device 1305 described with reference toFIG. 13. The device 1405 may also be a processor. The device 1405 mayinclude a receiver module 1410, a timing management module 1415, and atransmitter module 1420. Each of these components may be incommunication with each other.

The components of the device 1405 may, individually or collectively, beimplemented using one or more ASICs adapted to perform some or all ofthe applicable functions in hardware. Alternatively, the functions maybe performed by one or more other processing units (or cores), on one ormore integrated circuits. In other examples, other types of integratedcircuits may be used (e.g., Structured/Platform ASICs, FPGAs, and otherSemi-Custom ICs), which may be programmed in any manner known in theart. The functions of each unit may also be implemented, in whole or inpart, with instructions embodied in a memory, formatted to be executedby one or more general or application-specific processors.

In some examples, the receiver module 1410 may be or include an RFreceiver, such as an RF receiver operable to receive transmissions in afirst spectrum (e.g., a licensed LTE spectrum) or a second spectrum(e.g., a “shared spectrum” used by devices operating under differenttransmission protocols, such as an unlicensed spectrum). The RF receivermay include separate receivers for the first spectrum and the secondspectrum. The separate receivers may in some cases take the form of alicensed spectrum receiver module 1412 for communicating over the firstspectrum, and an unlicensed spectrum receiver module 1414 forcommunicating over the second spectrum. The receiver module 1410,including the licensed spectrum receiver module 1412 or the unlicensedspectrum receiver module 1414, may be used to receive various types ofdata or control signals (i.e., transmissions) over one or morecommunication links of a wireless communications system including thelicensed and unlicensed spectrums, such as one or more communicationlinks of the wireless communications system 100, 200, or 250 describedwith reference to FIG. 1, 2A, or 2B.

In some examples, the transmitter module 1420 may be or include an RFtransmitter, such as an RF transmitter operable to transmit in the firstspectrum or the second spectrum. The RF transmitter may include separatetransmitters for the first spectrum and the second spectrum. Theseparate transmitters may in some cases take the form of a licensedspectrum transmitter module 1422 for communicating over the firstspectrum, and an unlicensed spectrum transmitter module 1424 forcommunicating over the second spectrum. The transmitter module 1420,including the licensed spectrum transmitter module 1422 or theunlicensed spectrum transmitter module 1424, may be used to transmitvarious types of data or control signals (i.e., transmissions) over oneor more communication links of the wireless communications systemincluding the licensed spectrum and the unlicensed spectrum.

In some examples, the timing management module 1415 may be an example ofone or more aspects of the timing management module 1315 described withreference to FIG. 13 and may include a CET timing information analysismodule 1425 or a timing adjustment module 1430.

In some examples, the CET timing information analysis module 1425 may beused to receive at least one CET via the unlicensed spectrum receivermodule 1414 of the receiver module 1410. The at least one CET mayindicate timing information of at least a second device (e.g., a secondbase station) over a shared spectrum. The at least one CET may alsoindicate a timing stratum of at least the second device. In someexamples, the at least one CET may be received during a CET period.

In some examples, the at least one CET received by the CET timinginformation analysis module 1425 may include a first CET indicating thetiming information of the second device over the shared spectrum and asecond CET indicating timing information of a third device over theshared spectrum. The first CET and the second CET may be received at thedevice 1405 concurrently or at different times.

In some examples, the at least one CET may further indicate timinginformation for a third device over the shared spectrum. In theseexamples, the timing of the device 1405 may in some cases be adjustedbased on the timing information of the second device and the timinginformation of the third device. More generally, the timing of the firstdevice may be adjusted based on the timing information of any number ofdevices.

In some examples, the timing adjustment module 1430 may adjust a timingof the device 1405 based on the received timing information of at leastthe second device. The timing adjustment may include synchronizing atiming of the device 1405 to a timing of at least the second devicebased on the received timing information.

In some cases, the device 1405 and other devices from which the device1405 receives timing information may be members of a common PLMN. Inother cases, the device 1405 and other devices may be members ofdifferent PLMNs associated with different operators. The different PLMNsmay be synchronized with each other.

In some examples, the timing management module 1415 may further includea CET module 1435. The CET module 1435 may be used to transmit a CET ofthe device 1405 via the unlicensed spectrum transmitter module 1424 ofthe transmitter module 1420. The CET of the device 1405 may indicatetiming information of the device 1405 over the shared spectrum, as wellas provide an indication of a timing stratum of the device 1405.

In some examples, the at least one CET may be received at the device1405 during a particular CET period of a plurality of periodicallyscheduled CET periods. Each of the CET periods may include at least onePLMN-specific region and a common transmission region. In some cases,the timing information of at least the second base station may bereceived during the common transmission region of the particular CETperiod, or a CET of the first base station may be transmitted during thecommon transmission region.

FIG. 15 shows a block diagram 1500 of a device 1505 for use in wirelesscommunication, in accordance with various aspects of the presentdisclosure. In some examples, the device 1505 may be an example of oneor more aspects of one of the base stations 105 or 205 described withreference to FIG. 1 or 2, or the device 1305 or 1405 described withreference to FIG. 13 or 14. The device 1505 may also be a processor. Thedevice 1505 may include a receiver module 1510, a timing managementmodule 1515, and a transmitter module 1520. Each of these components maybe in communication with each other.

The components of the device 1505 may, individually or collectively, beimplemented using one or more ASICs adapted to perform some or all ofthe applicable functions in hardware. Alternatively, the functions maybe performed by one or more other processing units (or cores), on one ormore integrated circuits. In other examples, other types of integratedcircuits may be used (e.g., Structured/Platform ASICs, FPGAs, and otherSemi-Custom ICs), which may be programmed in any manner known in theart. The functions of each unit may also be implemented, in whole or inpart, with instructions embodied in a memory, formatted to be executedby one or more general or application-specific processors.

In some examples, the receiver module 1510 may be or include an RFreceiver, such as an RF receiver operable to receive transmissions in afirst spectrum (e.g., a licensed LTE spectrum) or a second spectrum(e.g., a “shared spectrum” used by devices operating under differenttransmission protocols, such as an unlicensed spectrum). The RF receivermay include separate receivers for the first spectrum and the secondspectrum. The separate receivers may in some cases take the form of alicensed spectrum receiver module 1512 for communicating over the firstspectrum, and an unlicensed spectrum receiver module 1514 forcommunicating over the second spectrum. The receiver module 1510,including the licensed spectrum receiver module 1512 or the unlicensedspectrum receiver module 1514, may be used to receive various types ofdata or control signals (i.e., transmissions) over one or morecommunication links of a wireless communications system including thelicensed and unlicensed spectrums, such as one or more communicationlinks of the wireless communications system 100, 200, or 250 describedwith reference to FIG. 1, 2A, or 2B.

In some examples, the transmitter module 1520 may be or include an RFtransmitter, such as an RF transmitter operable to transmit in the firstspectrum or the second spectrum. The RF transmitter may include separatetransmitters for the first spectrum and the second spectrum. Theseparate transmitters may in some cases take the form of a licensedspectrum transmitter module 1522 for communicating over the firstspectrum, and an unlicensed spectrum transmitter module 1524 forcommunicating over the second spectrum. The transmitter module 1520,including the licensed spectrum transmitter module 1522 or theunlicensed spectrum transmitter module 1524, may be used to transmitvarious types of data or control signals (i.e., transmissions) over oneor more communication links of the wireless communications systemincluding the licensed spectrum and the unlicensed spectrum.

The device 1505 presumes that CETs are transmitted or received during aCET period. The CET period may include a plurality of timingstratum-specific portions or a plurality of PLMN-specific portions, asdescribed, for example, with reference to FIG. 8. When a CET periodincludes a plurality of timing stratum-specific portions, each of thetiming stratum-specific portions may be assigned to one of a pluralityof timing stratums. When a CET period includes a plurality ofPLMN-specific portions, each of the PLMN-specific portions may beassigned to one of a plurality of PLMNs. When a CET period includes aplurality of timing stratum-specific portions and a plurality ofPLMN-specific portions, both a timing stratum-specific portion and aPLMN-specific portion may be assigned to a particular combination oftiming stratum and PLMN.

In some examples, the timing management module 1515 may be an example ofone or more aspects of the timing management module 1315 or 1415described with reference to FIG. 13 or 14 and may include a CET timinginformation analysis module 1525 or a timing adjustment module 1530.

In some examples, the CET timing information analysis module 1525 may bean example of one or more aspects of the CET timing information analysismodule 1425 described with reference to FIG. 14 and may include a CETperiod portion identification module 1540. The CET period portionidentification module 1540 may be used to identify a timingstratum-specific portion associated with a timing stratum of a seconddevice (e.g., a second base station) or a PLMN-specific portionassociated with a PLMN of the second device (i.e., both a timingstratum-specific portion associated with the timing stratum of thesecond device and a PLMN-specific portion associated with the PLMN ofthe second device, when both are available).

In some examples, the timing stratum-specific portion associated withthe timing stratum of the second device or the PLMN-specific portionassociated with the PLMN of the second device may be identified becausethe timing stratum associated with the second device is a lower stratumthan the timing stratum associated with the device 1505. In some cases,the timing stratum associated with the second device may be a next lowerstratum than the timing stratum associated with the device 1505.

In some examples, the CET timing information analysis module 1525 may beused to receive at least one CET via the unlicensed spectrum receivermodule 1514 of the receiver module 1510. Each of the at least one CETmay be received during a timing stratum-specific portion or aPLMN-specific portion of the CET period. The at least one CET mayindicate timing information of at least the second device over a sharedspectrum. The at least one CET may also indicate a timing stratum of atleast the second device. The timing information of the second device maybe received by listening to the identified timing stratum-specificportion or the identified PLMN-specific portion (i.e., both the timingstratum-specific portion associated with the timing stratum of thesecond device and the PLMN-specific portion associated with the PLMN ofthe second device, when both are available).

In some examples, the at least one CET received by the CET timinginformation analysis module 1525 may include a first CET indicating thetiming information of the second device over the shared spectrum and asecond CET indicating timing information of a third device over theshared spectrum. The first CET and the second CET may be received at thedevice 1505 concurrently (e.g., in the same timing stratum-specificportion or PLMN-specific portion of a CET period (i.e., both the sametiming stratum-specific portion and the same PLMN-specific portion, whenboth are available)) or at different times (e.g., in different timingstratum-specific portions or different PLMN-specific portions).

In some examples, the at least one CET may further indicate timinginformation for a third device over the shared spectrum. In theseexamples, the timing of the device 1505 may in some cases be adjustedbased on the timing information of the second device and the timinginformation of the third device. More generally, the timing of the firstdevice may be adjusted based on the timing information of any number ofdevices.

In some examples, the timing adjustment module 1530 may be an example ofone or more aspects of the timing adjustment module 1430 described withreference to FIG. 14. The timing adjustment module 1530 may be used toadjust a timing of the device 1505 based on the received timinginformation of at least the second device. The timing adjustment mayinclude synchronizing a timing of the device 1505 to a timing of atleast the second device based on the received timing information.

In some examples, the timing management module 1515 may further includea CET module 1535. The CET module 1535 may be used to transmit a CET ofthe device 1505. The CET of the device 1505 may indicate timinginformation of the device 1505 over the shared spectrum, as well asprovide an indication of a timing stratum of the device 1505.

FIG. 16 shows a block diagram 1600 of a device 1605 for use in wirelesscommunication, in accordance with various aspects of the presentdisclosure. In some examples, the device 1605 may be an example of oneor more aspects of one of the base stations 105 or 205 described withreference to FIG. 1 or 2, or the device 1305 or 1405 described withreference to FIG. 13 or 14. The device 1605 may also be a processor. Thedevice 1605 may include a receiver module 1610, a timing managementmodule 1615, and a transmitter module 1620. Each of these components maybe in communication with each other.

The components of the device 1605 may, individually or collectively, beimplemented using one or more ASICs adapted to perform some or all ofthe applicable functions in hardware. Alternatively, the functions maybe performed by one or more other processing units (or cores), on one ormore integrated circuits. In other examples, other types of integratedcircuits may be used (e.g., Structured/Platform ASICs, FPGAs, and otherSemi-Custom ICs), which may be programmed in any manner known in theart. The functions of each unit may also be implemented, in whole or inpart, with instructions embodied in a memory, formatted to be executedby one or more general or application-specific processors.

In some examples, the receiver module 1610 may be or include an RFreceiver, such as an RF receiver operable to receive transmissions in afirst spectrum (e.g., a licensed LTE spectrum) or a second spectrum(e.g., a “shared spectrum” used by devices operating under differenttransmission protocols, such as an unlicensed spectrum). The RF receivermay include separate receivers for the first spectrum and the secondspectrum. The separate receivers may in some cases take the form of alicensed spectrum receiver module 1612 for communicating over the firstspectrum, and an unlicensed spectrum receiver module 1614 forcommunicating over the second spectrum. The receiver module 1610,including the licensed spectrum receiver module 1612 or the unlicensedspectrum receiver module 1614, may be used to receive various types ofdata or control signals (i.e., transmissions) over one or morecommunication links of a wireless communications system including thelicensed and unlicensed spectrums, such as one or more communicationlinks of the wireless communications system 100, 200, or 250 describedwith reference to FIG. 1, 2A, or 2B.

In some examples, the transmitter module 1620 may be or include an RFtransmitter, such as an RF transmitter operable to transmit in the firstspectrum or the second spectrum. The RF transmitter may include separatetransmitters for the first spectrum and the second spectrum. Theseparate transmitters may in some cases take the form of a licensedspectrum transmitter module 1622 for communicating over the firstspectrum, and an unlicensed spectrum transmitter module 1624 forcommunicating over the second spectrum. The transmitter module 1620,including the licensed spectrum transmitter module 1622 or theunlicensed spectrum transmitter module 1624, may be used to transmitvarious types of data or control signals (i.e., transmissions) over oneor more communication links of the wireless communications systemincluding the licensed spectrum and the unlicensed spectrum.

The device 1605 presumes that CETs are transmitted or received during aCET period. The CET period may be one of a plurality of periodicallyscheduled CET periods, in which each of the plurality of periodicallyscheduled CET periods may include a plurality of PLMN-specific regionsand a common transmission region, as described, for example, withreference to FIG. 10. The PLMN-specific regions of each CET period mayhave a time rank order, and PLMN-specific regions of different time rankmay be assigned to different PLMNs in different CET periods. Likewise,the common transmission regions of different CET periods may be assignedto different PLMNs in different CET periods. In some cases, thePLMN-specific regions or the common transmission regions may be assignedto different PLMNs in different CET periods on a rotating basis.

In some examples, the timing management module 1615 may be an example ofone or more aspects of the timing management module 1315 or 1415described with reference to FIG. 13 or 14 and may include a CET timinginformation analysis module 1625 or a timing adjustment module 1630.

In some examples, the CET timing information analysis module 1625 may bean example of one or more aspects of the CET timing information analysismodule 1425 described with reference to FIG. 14 and may include a PLMNassignment determination module 1640. The CET timing informationanalysis module 1625 may be used to receive at least one CET via theunlicensed spectrum receiver module 1614 of the receiver module 1610.Each of the at least one CET may be received during a particular CETperiod of the plurality of periodically scheduled CET periods. The atleast one CET may indicate timing information of at least a seconddevice (e.g., a second base station) over a shared spectrum. The atleast one CET may also indicate a timing stratum of at least the seconddevice. In some cases, the timing information of at least the seconddevice may be received during one of the PLMN-specific regions. In othercases, the timing information of at least the second device may bereceived during the common transmission region.

In some examples, the PLMN assignment determination module 1640 may beused to determine the PLMN assignments of the PLMN-specific regions orcommon transmission region for a particular CET period. Thedetermination may include a determination of which PLMN-specific regionis assigned to the PLMN of the second device, as well as a determinationof whether the common transmission region is assigned to the PLMN of thesecond device. In some cases, it may be determined (e.g., inferred) thatthe common transmission region is assigned to the PLMN of the seconddevice based on an assignment of a PLMN-specific region having aparticular time rank (e.g., the last PLMN-specific region in time rankorder) to the PLMN of the second device for the particular CET period.

In some examples, the timing adjustment module 1630 may be used toadjust a timing of the device 1605 based on the received timinginformation of at least the second device. The timing adjustment mayinclude synchronizing a timing of the device 1605 to a timing of atleast the second device based on the received timing information.

In some examples, the at least one CET received by the CET timinginformation analysis module 1625 may include a first CET indicating thetiming information of the second device over the shared spectrum and asecond CET indicating timing information of a third device over theshared spectrum. The first CET and the second CET may be received at thedevice 1605 concurrently or at different times.

In some examples, the at least one CET may further indicate timinginformation for a third device over the shared spectrum. In theseexamples, the timing of the device 1605 may in some cases be adjustedbased on the timing information of the second device and the timinginformation of the third device. More generally, the timing of the firstdevice may be adjusted based on the timing information of any number ofdevices.

In some cases, the first base station and the second base station may bemembers of a common PLMN. In other cases, the first base station and thesecond base station may be members of different PLMNs associated withdifferent operators. The different PLMNs may be synchronized with eachother.

In some examples, the timing management module 1615 may further includea CET module 1635. The CET module 1635 may be used to transmit a CET ofthe device 1605. The CET of the device 1605 may indicate timinginformation of the device 1605 over the shared spectrum, as well asprovide an indication of a timing stratum of the device 1605.

FIG. 17 shows a block diagram 1700 of a device 1705 for use in wirelesscommunication, in accordance with various aspects of the presentdisclosure. In some examples, the device 1705 may be an example of oneor more aspects of one of the base stations 105 or 205 described withreference to FIG. 1 or 2, or the device 1305 or 1405 described withreference to FIG. 13 or 14. The device 1705 may also be a processor. Thedevice 1705 may include a receiver module 1710, a timing managementmodule 1715, and a transmitter module 1720. Each of these components maybe in communication with each other.

The components of the device 1705 may, individually or collectively, beimplemented using one or more ASICs adapted to perform some or all ofthe applicable functions in hardware. Alternatively, the functions maybe performed by one or more other processing units (or cores), on one ormore integrated circuits. In other examples, other types of integratedcircuits may be used (e.g., Structured/Platform ASICs, FPGAs, and otherSemi-Custom ICs), which may be programmed in any manner known in theart. The functions of each unit may also be implemented, in whole or inpart, with instructions embodied in a memory, formatted to be executedby one or more general or application-specific processors.

In some examples, the receiver module 1710 may be or include an RFreceiver, such as an RF receiver operable to receive transmissions in afirst spectrum (e.g., a licensed LTE spectrum) or a second spectrum(e.g., a “shared spectrum” used by devices operating under differenttransmission protocols, such as an unlicensed spectrum). The RF receivermay include separate receivers for the first spectrum and the secondspectrum. The separate receivers may in some cases take the form of alicensed spectrum receiver module 1712 for communicating over the firstspectrum, and an unlicensed spectrum receiver module 1714 forcommunicating over the second spectrum. The receiver module 1710,including the licensed spectrum receiver module 1712 or the unlicensedspectrum receiver module 1714, may be used to receive various types ofdata or control signals (i.e., transmissions) over one or morecommunication links of a wireless communications system including thelicensed and unlicensed spectrums, such as one or more communicationlinks of the wireless communications system 100, 200, or 250 describedwith reference to FIG. 1, 2A, or 2B.

In some examples, the transmitter module 1720 may be or include an RFtransmitter, such as an RF transmitter operable to transmit in the firstspectrum or the second spectrum. The RF transmitter may include separatetransmitters for the first spectrum and the second spectrum. Theseparate transmitters may in some cases take the form of a licensedspectrum transmitter module 1722 for communicating over the firstspectrum, and an unlicensed spectrum transmitter module 1724 forcommunicating over the second spectrum. The transmitter module 1720,including the licensed spectrum transmitter module 1722 or theunlicensed spectrum transmitter module 1724, may be used to transmitvarious types of data or control signals (i.e., transmissions) over oneor more communication links of the wireless communications systemincluding the licensed spectrum and the unlicensed spectrum.

The device 1705 presumes that CETs are transmitted or received during aCET period. The CET period may be one of a plurality of periodicallyscheduled CET periods, in which each of the plurality of periodicallyscheduled CET periods may include a plurality of PLMN-specific regionsand a common transmission region, as described, for example, withreference to FIG. 10. The PLMN-specific regions of each CET period mayhave a time rank order, and PLMN-specific regions of different time rankmay be assigned to different PLMNs in different CET periods. The commontransmission regions of different CET periods may be assigned todifferent combinations of PLMNs and timing stratums in different CETperiods. In some cases, the PLMN-specific regions may be assigned todifferent PLMNs in different CET periods on a rotating basis. Likewise,the common transmission regions may be assigned to differentcombinations of PLMNs and timing stratums in different CET periods on arotating basis.

In some examples, the timing management module 1715 may be an example ofone or more aspects of the timing management module 1315 or 1415described with reference to FIG. 13 or 14 and may include a CET timinginformation analysis module 1725 or a timing adjustment module 1730.

In some examples, the CET timing information analysis module 1725 may bean example of one or more aspects of the CET timing information analysismodule 1425 described with reference to FIG. 14 and may include a PLMNassignment determination module 1740 or a timing source selection module1745. The CET timing information analysis module 1725 may be used toreceive at least one CET via the unlicensed spectrum receiver module1714 of the receiver module 1710. Each of the at least one CET may bereceived during a particular CET period of the plurality of periodicallyscheduled CET periods. The at least one CET may indicate timinginformation of at least a second device (e.g., a second base station)over a shared spectrum. The at least one CET may also indicate a timingstratum of at least the second device. In some cases, the timinginformation of at least the second device may be received during one ofthe PLMN-specific regions. In other cases, the timing information of atleast the second device may be received during the common transmissionregion.

In some examples, the PLMN assignment determination module 1740 may beused to determine the PLMN assignments of the PLMN-specific regions orcommon transmission region for a particular CET period. Thedetermination may include a determination of which PLMN-specific regionis assigned to the PLMN of the second device, as well as a determinationof whether the common transmission region is assigned to the PLMN of thesecond device. In some cases, it may be determined (e.g., inferred) thatthe common transmission region is assigned to the PLMN of the seconddevice based on an assignment of a PLMN-specific region having aparticular time rank (e.g., the last PLMN-specific region in time rankorder) to the PLMN of the second device for the particular CET period.

In some examples, the timing source selection module 1745 may be used todetermine that the second device includes a compatible timing stratumsynchronization source for the device 1705. In some cases, the seconddevice may be determined to include a compatible timing stratumsynchronization source because the timing stratum associated with thesecond device is a lower stratum than the timing stratum associated withthe device 1705. In some cases, the second device may be determined toinclude a compatible timing stratum synchronization source because thetiming stratum associated with the second device is a next lower stratumthan the timing stratum associated with the device 1705. The timingsource selection module 1745 may also be used to select the seconddevice, based on the aforesaid determination, as a basis for adjustingthe timing of the device 1705.

In some examples, the timing adjustment module 1730 may be used toadjust a timing of the device 1705 based on the received timinginformation of at least the second device. The timing adjustment mayinclude synchronizing a timing of the device 1705 to a timing of atleast the second device based on the received timing information.

In some examples, the at least one CET received by the CET timinginformation analysis module 1725 may include a first CET indicating thetiming information of the second device over the shared spectrum and asecond CET indicating timing information of a third device over theshared spectrum. The first CET and the second CET may be received at thedevice 1705 concurrently or at different times.

In some examples, the at least one CET may further indicate timinginformation for a third device over the shared spectrum. In theseexamples, the timing of the device 1705 may in some cases be adjustedbased on the timing information of the second device and the timinginformation of the third device. More generally, the timing of the firstdevice may be adjusted based on the timing information of any number ofdevices.

In some cases, the first base station and the second base station may bemembers of a common PLMN. In other cases, the first base station and thesecond base station may be members of different PLMNs associated withdifferent operators. The different PLMNs may be synchronized with eachother.

In some examples, the timing management module 1715 may further includea CET module 1735. The CET module 1735 may be used to transmit a CET ofthe device 1705. The CET of the device 1705 may indicate timinginformation of the device 1705 over the shared spectrum, as well asprovide an indication of a timing stratum of the device 1705.

FIG. 18 shows a block diagram 1800 of a device 1805 for use in wirelesscommunication, in accordance with various aspects of the presentdisclosure. In some examples, the device 1805 may be an example of oneor more aspects of one of the base stations 105 or 205 described withreference to FIG. 1 or 2, or the device 1305 or 1405 described withreference to FIG. 13 or 14. The device 1805 may also be a processor. Thedevice 1805 may include a receiver module 1810, a timing managementmodule 1815, and a transmitter module 1820. Each of these components maybe in communication with each other.

The components of the device 1805 may, individually or collectively, beimplemented using one or more ASICs adapted to perform some or all ofthe applicable functions in hardware. Alternatively, the functions maybe performed by one or more other processing units (or cores), on one ormore integrated circuits. In other examples, other types of integratedcircuits may be used (e.g., Structured/Platform ASICs, FPGAs, and otherSemi-Custom ICs), which may be programmed in any manner known in theart. The functions of each unit may also be implemented, in whole or inpart, with instructions embodied in a memory, formatted to be executedby one or more general or application-specific processors.

In some examples, the receiver module 1810 may be or include an RFreceiver, such as an RF receiver operable to receive transmissions in afirst spectrum (e.g., a licensed LTE spectrum) or a second spectrum(e.g., a “shared spectrum” used by devices operating under differenttransmission protocols, such as an unlicensed spectrum). The RF receivermay include separate receivers for the first spectrum and the secondspectrum. The separate receivers may in some cases take the form of alicensed spectrum receiver module 1812 for communicating over the firstspectrum, and an unlicensed spectrum receiver module 1814 forcommunicating over the second spectrum. The receiver module 1810,including the licensed spectrum receiver module 1812 or the unlicensedspectrum receiver module 1814, may be used to receive various types ofdata or control signals (i.e., transmissions) over one or morecommunication links of a wireless communications system including thelicensed and unlicensed spectrums, such as one or more communicationlinks of the wireless communications system 100, 200, or 250 describedwith reference to FIG. 1, 2A, or 2B.

In some examples, the transmitter module 1820 may be or include an RFtransmitter, such as an RF transmitter operable to transmit in the firstspectrum or the second spectrum. The RF transmitter may include separatetransmitters for the first spectrum and the second spectrum. Theseparate transmitters may in some cases take the form of a licensedspectrum transmitter module 1822 for communicating over the firstspectrum, and an unlicensed spectrum transmitter module 1824 forcommunicating over the second spectrum. The transmitter module 1820,including the licensed spectrum transmitter module 1822 or theunlicensed spectrum transmitter module 1824, may be used to transmitvarious types of data or control signals (i.e., transmissions) over oneor more communication links of the wireless communications systemincluding the licensed spectrum and the unlicensed spectrum.

The device 1805 presumes that the device 1805 and at least a seconddevice (e.g., at least a second base station) share a periodic CETtiming. Because of the shared CET timing, the transmission of a CET bythe device 1805 may interfere with the device's receipt of a CET of atleast the second device (e.g., because the respective CETs may bereceived and transmitted concurrently).

In some examples, the timing management module 1815 may be an example ofone or more aspects of the timing management module 1315 or 1415described with reference to FIG. 13 or 14 and may include a CET timinginformation analysis module 1825, a timing adjustment module 1830, or aCET module 1835.

In some examples, the CET timing information analysis module 1825 may bean example of one or more aspects of the CET timing information analysismodule 1425 described with reference to FIG. 14 and may include a gatingmodule 1840 or a timing stratum determination module 1845. The gatingmodule 1840 may be used to access a periodic gating schedule todetermine whether the CET of the device 1805 should be gated (i.e., nottransmitted) in a current CET period. The periodic gating schedule mayindicate particular CET period(s) in which the CET of the device 1805should be gated to mitigate interference with the device's receipt ofthe CET of at least a second device (e.g., a second base station).

In some examples, the timing stratum determination module 1845 may beused to determine a timing stratum of the device 1805.

In some examples, the CET timing information analysis module 1825 may beused to receive at least one CET via the unlicensed spectrum receivermodule 1814 of the receiver module 1810. Each of the at least one CETmay be received during a current CET period of a plurality ofperiodically scheduled CET periods. The at least one CET may indicatetiming information of at least a second device (e.g., a second basestation) over a shared spectrum. The at least one CET may also indicatea timing stratum of at least the second device.

In some examples, the timing adjustment module 1830 may be used toadjust a timing of the device 1805 based on the received timinginformation of at least the second device. The timing adjustment mayinclude synchronizing a timing of the device 1805 to a timing of atleast the second device based on the received timing information.

In some examples, the at least one CET received by the CET timinginformation analysis module 1825 may include a first CET indicating thetiming information of the second device over the shared spectrum and asecond CET indicating timing information of a third device over theshared spectrum. The first CET and the second CET may be received at thedevice 1805 concurrently or at different times.

In some examples, the at least one CET may further indicate timinginformation for a third device over the shared spectrum. In theseexamples, the timing of the device 1805 may in some cases be adjustedbased on the timing information of the second device and the timinginformation of the third device. More generally, the timing of the firstdevice may be adjusted based on the timing information of any number ofdevices.

In some cases, the first base station and the second base station may bemembers of a common PLMN. In other cases, the first base station and thesecond base station may be members of different PLMNs associated withdifferent operators. The different PLMNs may be synchronized with eachother.

In some examples, the CET module 1835 may be used to transmit a CET ofthe device 1805. The CET of the device 1805 may indicate timinginformation of the device 1805 over the shared spectrum, as well asprovide an indication of a timing stratum of the device 1805. The CETmodule 1835 may be prohibited from transmitting a CET of the device 1805in CET periods gated by the gating module 1840.

In some examples, the at least one CET may be received during aparticular CET period of a plurality of periodically scheduled CETperiods. Each of the CET periods may include at least one PLMN-specificregion and a common transmission region. In some cases, the timinginformation of at least the second device may be received during thecommon transmission region of the particular CET period or a CET of thedevice 1805 may be transmitted during the common transmission region.

FIG. 19 shows a block diagram 1900 of a device 1905 for use in wirelesscommunication, in accordance with various aspects of the presentdisclosure. In some examples, the device 1905 may be an example of oneor more aspects of one of the base stations 105 or 205 described withreference to FIG. 1 or 2, or the device 1305 described with reference toFIG. 13. The device 1905 may also be a processor. The device 1905 mayinclude a receiver module 1910, a timing management module 1915, and atransmitter module 1920. Each of these components may be incommunication with each other.

The components of the device 1905 may, individually or collectively, beimplemented using one or more ASICs adapted to perform some or all ofthe applicable functions in hardware. Alternatively, the functions maybe performed by one or more other processing units (or cores), on one ormore integrated circuits. In other examples, other types of integratedcircuits may be used (e.g., Structured/Platform ASICs, FPGAs, and otherSemi-Custom ICs), which may be programmed in any manner known in theart. The functions of each unit may also be implemented, in whole or inpart, with instructions embodied in a memory, formatted to be executedby one or more general or application-specific processors.

In some examples, the receiver module 1910 may be or include an RFreceiver, such as an RF receiver operable to receive transmissions in afirst spectrum (e.g., a licensed LTE spectrum) or a second spectrum(e.g., a “shared spectrum” used by devices operating under differenttransmission protocols, such as an unlicensed spectrum). The RF receivermay include separate receivers for the first spectrum and the secondspectrum. The separate receivers may in some cases take the form of alicensed spectrum receiver module 1912 for communicating over the firstspectrum, and an unlicensed spectrum receiver module 1914 forcommunicating over the second spectrum. The receiver module 1910,including the licensed spectrum receiver module 1912 or the unlicensedspectrum receiver module 1914, may be used to receive various types ofdata or control signals (i.e., transmissions) over one or morecommunication links of a wireless communications system including thelicensed and unlicensed spectrums, such as one or more communicationlinks of the wireless communications system 100, 200, or 250 describedwith reference to FIG. 1, 2A, or 2B.

In some examples, the transmitter module 1920 may be or include an RFtransmitter, such as an RF transmitter operable to transmit in the firstspectrum or the second spectrum. The RF transmitter may include separatetransmitters for the first spectrum and the second spectrum. Theseparate transmitters may in some cases take the form of a licensedspectrum transmitter module 1922 for communicating over the firstspectrum, and an unlicensed spectrum transmitter module 1924 forcommunicating over the second spectrum. The transmitter module 1920,including the licensed spectrum transmitter module 1922 or theunlicensed spectrum transmitter module 1924, may be used to transmitvarious types of data or control signals (i.e., transmissions) over oneor more communication links of the wireless communications systemincluding the licensed spectrum and the unlicensed spectrum.

In some examples, the timing management module 1915 may be an example ofone or more aspects of the timing management module 1315 described withreference to FIG. 13 and may include a CCA slot identification module1925, a CCA module 1930, a timing transmission module 1935, or a timingreception module 1940.

In some examples, the CCA slot identification module 1925 may be used toidentify a CCA slot assigned to the device 1905 for a frame of a sharedspectrum. The frame may be a frame associated with time synchronization,as described, for example, with reference to FIG. 11. In some cases, theframe may be one of a plurality of periodic sync frames.

In some examples, the CCA slot assigned to the first base station for aframe of the shared spectrum may be identified based on a timing stratumof the first base station

In some examples, the CCA slot assigned to the first base station mayoccur earlier in a frame than one or more CCA slots associated withtiming stratums that are higher than the timing stratum of the firstbase station (e.g., if the first base station is associated with a lowertiming stratum and is a GPS source, or is associated with a timingstratum that is closer to a GPS source in a synchronization stratum thanother base stations, the first base station may perform CCA in a CCAslot that occurs earlier in a frame than one or more other CCA slots).In general, base stations associated with lower timing stratums may beassigned CCA slots that occur earlier in a frame.

In some examples, the CCA module 1930 may be used to perform a CCA atthe CCA slot identified for the frame by the CCA slot identificationmodule 1925.

In some examples (e.g., when the CCA is successful), the timingtransmission module 1935 may be used to selectively transmit a firsttiming information of the device 1905.

In some examples (e.g., when the CCA is unsuccessful), the timingreception module 1940 may be used to listen for a second timinginformation of a second device (e.g., a second base station) during theframe. In some cases, the timing reception module 1940 may also listenfor a third timing information of a third device during the frame (orlisten for and receive additional timing information of additionaldevices). The second timing information and the third timing information(as well as other timing information) may in some cases be receivedconcurrently.

FIG. 20 shows a block diagram 2000 of a device 2005 for use in wirelesscommunication, in accordance with various aspects of the presentdisclosure. In some examples, the device 2005 may be an example of oneor more aspects of one of the base stations 105 or 205 described withreference to FIG. 1 or 2, or the device 1305 described with reference toFIG. 13. The device 2005 may also be a processor. The device 2005 mayinclude a receiver module 2010, a timing management module 2015, and atransmitter module 2020. Each of these components may be incommunication with each other.

The components of the device 2005 may, individually or collectively, beimplemented using one or more ASICs adapted to perform some or all ofthe applicable functions in hardware. Alternatively, the functions maybe performed by one or more other processing units (or cores), on one ormore integrated circuits. In other examples, other types of integratedcircuits may be used (e.g., Structured/Platform ASICs, FPGAs, and otherSemi-Custom ICs), which may be programmed in any manner known in theart. The functions of each unit may also be implemented, in whole or inpart, with instructions embodied in a memory, formatted to be executedby one or more general or application-specific processors.

In some examples, the receiver module 2010 may be or include an RFreceiver, such as an RF receiver operable to receive transmissions in afirst spectrum (e.g., a licensed LTE spectrum) or a second spectrum(e.g., a “shared spectrum” used by devices operating under differenttransmission protocols, such as an unlicensed spectrum). The RF receivermay include separate receivers for the first spectrum and the secondspectrum. The separate receivers may in some cases take the form of alicensed spectrum receiver module 2012 for communicating over the firstspectrum, and an unlicensed spectrum receiver module 2014 forcommunicating over the second spectrum. The receiver module 2010,including the licensed spectrum receiver module 2012 or the unlicensedspectrum receiver module 2014, may be used to receive various types ofdata or control signals (i.e., transmissions) over one or morecommunication links of a wireless communications system including thelicensed and unlicensed spectrums, such as one or more communicationlinks of the wireless communications system 100, 200, or 250 describedwith reference to FIG. 1, 2A, or 2B.

In some examples, the transmitter module 2020 may be or include an RFtransmitter, such as an RF transmitter operable to transmit in the firstspectrum or the second spectrum. The RF transmitter may include separatetransmitters for the first spectrum and the second spectrum. Theseparate transmitters may in some cases take the form of a licensedspectrum transmitter module 2022 for communicating over the firstspectrum, and an unlicensed spectrum transmitter module 2024 forcommunicating over the second spectrum. The transmitter module 2020,including the licensed spectrum transmitter module 2022 or theunlicensed spectrum transmitter module 2024, may be used to transmitvarious types of data or control signals (i.e., transmissions) over oneor more communication links of the wireless communications systemincluding the licensed spectrum and the unlicensed spectrum.

In some examples, the timing management module 2015 may be an example ofone or more aspects of the timing management module 1315 described withreference to FIG. 13 and may include a CCA slot identification module2025, a CCA module 2030, a timing transmission module 2035, or a timingreception module 2040.

In some examples, the CCA slot identification module 2025 may be used toidentify a CCA slot assigned to the device 2005 for a frame of a sharedspectrum. The frame may be a frame associated with time synchronization.In some cases, the frame may be one of a plurality of periodic syncframes. In some cases, a timing of the CCA slot assigned to the firstbase station may be delayed with respect to a CCA period associated witha CCA slot assigned to a base station having a timing stratum that islower than a timing stratum of the first base station, as described, forexample, with reference to FIG. 12.

In some examples, the CCA slot assigned to the first base station for aframe of the shared spectrum may be identified based on a timing stratumof the first base station

In some examples, the CCA slot assigned to the first base station mayoccur earlier in a frame than one or more CCA slots associated withtiming stratums that are higher than the timing stratum of the firstbase station (e.g., if the first base station is associated with a lowertiming stratum and is a GPS source, or is associated with a timingstratum that is closer to a GPS source in a synchronization stratum thanother base stations, the first base station may perform CCA in a CCAslot that occurs earlier in a frame than one or more other CCA slots).In general, base stations associated with lower timing stratums may beassigned CCA slots that occur earlier in a frame. However, when thefirst base station is associated with a higher stratum and the timing ofthe CCA slot assigned to the first base station is delayed with respectto a CCA period associated with a CCA slot assigned to a base stationhaving a lower timing stratum, the delay may enable the first basestation to gain access to the shared spectrum regardless of another basestation gaining access to the shared spectrum during an earlier part ofthe frame.

In some examples, the CCA module 2030 may be used to perform a CCA atthe CCA slot identified for the frame by the CCA slot identificationmodule 2025.

In some examples (e.g., when the CCA is successful), the timingtransmission module 2035 may be used to selectively transmit a firsttiming information of the device 2005.

In some examples (e.g., when the CCA is unsuccessful), the timingreception module 2040 may be used to listen for a second timinginformation of a second device (e.g., a second base station) during theframe. In some cases, the timing reception module 2040 may also listenfor a third timing information of a third device during the frame (orlisten for and receive additional timing information of additionaldevices). The second timing information and the third timing information(as well as other timing information) may in some cases be receivedconcurrently.

FIG. 21 shows a block diagram 2100 of a device 2105 for use in wirelesscommunication, in accordance with various aspects of the presentdisclosure. In some examples, the device 2105 may be an example of oneor more aspects of one of the base stations 105 or 205 described withreference to FIG. 1 or 2, or the device 1305, 1905, or 2005 describedwith reference to FIG. 13, 19, or 20. The device 2105 may also be aprocessor.

The device 2105 may include a receiver module 2110, a timing managementmodule 2115, and a transmitter module 2120. Each of these components maybe in communication with each other.

The components of the device 2105 may, individually or collectively, beimplemented using one or more ASICs adapted to perform some or all ofthe applicable functions in hardware. Alternatively, the functions maybe performed by one or more other processing units (or cores), on one ormore integrated circuits. In other examples, other types of integratedcircuits may be used (e.g., Structured/Platform ASICs, FPGAs, and otherSemi-Custom ICs), which may be programmed in any manner known in theart. The functions of each unit may also be implemented, in whole or inpart, with instructions embodied in a memory, formatted to be executedby one or more general or application-specific processors.

In some examples, the receiver module 2110 may be or include an RFreceiver, such as an RF receiver operable to receive transmissions in afirst spectrum (e.g., a licensed LTE spectrum) or a second spectrum(e.g., a “shared spectrum” used by devices operating under differenttransmission protocols, such as an unlicensed spectrum). The RF receivermay include separate receivers for the first spectrum and the secondspectrum. The separate receivers may in some cases take the form of alicensed spectrum receiver module 2112 for communicating over the firstspectrum, and an unlicensed spectrum receiver module 2114 forcommunicating over the second spectrum. The receiver module 2110,including the licensed spectrum receiver module 2112 or the unlicensedspectrum receiver module 2114, may be used to receive various types ofdata or control signals (i.e., transmissions) over one or morecommunication links of a wireless communications system including thelicensed and unlicensed spectrums, such as one or more communicationlinks of the wireless communications system 100, 200, or 250 describedwith reference to FIG. 1, 2A, or 2B.

In some examples, the transmitter module 2120 may be or include an RFtransmitter, such as an RF transmitter operable to transmit in the firstspectrum or the second spectrum. The RF transmitter may include separatetransmitters for the first spectrum and the second spectrum. Theseparate transmitters may in some cases take the form of a licensedspectrum transmitter module 2122 for communicating over the firstspectrum, and an unlicensed spectrum transmitter module 2124 forcommunicating over the second spectrum.

The transmitter module 2120, including the licensed spectrum transmittermodule 2122 or the unlicensed spectrum transmitter module 2124, may beused to transmit various types of data or control signals (i.e.,transmissions) over one or more communication links of the wirelesscommunications system including the licensed spectrum and the unlicensedspectrum.

In some examples, the timing management module 2115 may be an example ofone or more aspects of the timing management module 1315 or 1915described with reference to FIG. 13 or 19 and may include a CCA slotidentification module 2125, a CCA module 2130, a timing transmissionmodule 2135, a timing reception module 2140, a data transmission module2145, or a timing adjustment module 2150.

In some examples, the CCA slot identification module 2125 may be used toidentify a CCA slot assigned to the device 2105 for a frame of a sharedspectrum. The frame may be associated with time synchronization, asdescribed, for example, with reference to FIG. 11 or 12.

In some examples, the CCA slot assigned to the first base station for aframe of a shared spectrum may be identified based on a timing stratumof the first base station

In some examples, the CCA slot assigned to the first base station may beearlier than one or more CCA slots associated with timing stratums thatare higher than the timing stratum of the first base station (e.g., ifthe first base station is associated with a lower timing stratum and isa GPS source, or is associated with a timing stratum that is closer to aGPS source in a synchronization stratum than other base stations, thefirst base station may perform CCA in a CCA slot that occurs earlierthan one or more other CCA slots).

In some examples, a CCA slot timing of the first base station may bedelayed based on a timing stratum of the first base station, asdescribed, for example, with reference to FIG. 12.

In some examples, the CCA module 2130 may be used to perform a CCA atthe CCA slot identified for the frame by the CCA slot identificationmodule 2125.

The timing transmission module 2135 may be an example of the timingtransmission module 1935 or 2035 described with reference to FIG. 19 or20. In some examples (e.g., when a CCA performed by the CCA module 2130is successful), the timing transmission module 2135 may be used toselectively transmit a first timing information of the device 2105. Thefirst timing information may in some cases be transmitted during atleast one reference signal resource element of a frame for which CCA issuccessful.

The timing reception module 2140 may be an example of the timingreception module 1940 or 2040 described with reference to FIG. 19 or 20.In some examples (e.g., when a CCA performed by the CCA module 2130 isunsuccessful), the timing reception module 2140 may be used to listenfor a second timing information of a second device (e.g., a second basestation), during a frame for which CCA is successful, by listening for achannel usage beacon signal from the second device. In some cases, thetiming reception module 2140 may also listen for a third timinginformation of a third base station during the frame (or listen for andreceive additional timing information of additional base station). Thesecond timing information and the third timing information (as well asother timing information) may in some cases be received concurrently.

The data transmission module 2145 may be used to transmit data to atleast one UE during a frame for which CCA is successful. The data may insome cases be transmitted to the at least one UE concurrent with thetransmission of the first timing information transmitted by the timingtransmission module 2135.

The timing adjustment module 2150 may be used to adjust a timing of thedevice 2105 based on the second timing information. In some cases, thetiming of the device 2105 may also be adjusted based on a third timinginformation received from a third device, or on timing informationreceived from any number of devices. The timing information receivedfrom the third device may be received during the same or a differentframe in which the second timing information is received.

In some examples, the timing adjustment module 2150 may determine atiming of the second device based on the second timing information, andthe timing of the device 2105 may be adjusted by synchronizing thetiming of the device 2105 to the timing of the second device.

FIG. 22 is a message flow diagram 2200 illustrating wirelesscommunication between a first base station 2205-a and a second basestation 2205-b. The first base station 2205-a may in some cases beassociated with a higher timing stratum (e.g., TS2) than the timingstratum (e.g., TS1) of the second base station 2205-b. In some cases,the first base station 2205-a and the second base station 2205-b may bemembers of a common PLMN. In other cases, the first base station 2205-aand the second base station 2205-b may be members of different PLMNsassociated with different operators. The different PLMNs may besynchronized with each other.

In some examples, each of the first base station 2205-a or the secondbase station 2205-b may be an example of one or more aspects of the basestation 105 or 205 described with reference to FIG. 1 or 2, or thedevice 1305, 1405, 1505, 1605, 1705, or 1805 described with reference toFIG. 13, 14, 15, 16, 17, or 18.

By way of example, the message flow may begin during a CET period 2210.During the CET period 2210, the first base station 2205-a may be in alisten mode 2215. While in the listen mode 2215, the first base station2205-a may receive at least one CET indicating timing information of atleast the second base station 2205-b over a shared spectrum. The atleast one CET may also indicate a timing stratum of at least the secondbase station 2205-b. The at least one CET may include a CET 2220 of thesecond base station 2205-b.

As shown, the first base station 2205-a may in some cases receive a CET2225 of a third base station or other base stations. The CET 2225 of thethird base station may be received concurrently with, or at a differenttime than, the CET 2220 of the second base station 2205-b. The firstbase station 2205-a may also transmit its own CET 2230 during its listenmode 2215, which CET 2230 may indicate timing information of the firstbase station 2205-a over the shared spectrum as well as a timing stratumof the first base station 2205-a.

At block 2235, a timing of the first base station 2205-a may be adjustedbased on the received timing information of at least the second basestation 2205-b. In some cases, the timing adjustment may includesynchronizing a timing of the first base station 2205-a to a timing ofat least the second base station 2205-b based on the received timinginformation. The timing of the first base station 2205-a may also besynchronized with other base stations, such as the third base station.

FIG. 23 is a message flow diagram 2300 illustrating wirelesscommunication between a first base station 2305-a and a second basestation 2305-b. The first base station 2305-a may in some cases beassociated with a higher timing stratum (e.g., TS2) than the timingstratum (e.g., TS1) of the second base station 2305-b. In some cases,the first base station 2305-a and the second base station 2305-b may bemembers of a common PLMN. In other cases, the first base station 2305-aand the second base station 2305-b may be members of different PLMNsassociated with different operators. The different PLMNs may besynchronized with each other.

In some examples, each of the first base station 2305-a or the secondbase station 2305-b may be an example of one or more aspects of the basestation 105 or 205 described with reference to FIG. 1 or 2, or thedevice 1305, 1405, or 1505 described with reference to FIG. 13, 14, or15.

By way of example, the message flow may begin at block 2310, with thefirst base station 2305-a identifying, within a CET period 2315, atiming stratum-specific portion associated with a timing stratum of thesecond base station 2305-b or a PLMN-specific portion associated with aPLMN of the second base station 2305-b (i.e., both a timingstratum-specific portion associated with the timing stratum of thesecond base station 2305-b and a PLMN-specific portion associated withthe PLMN of the second base station 2305-b, when both are available). Insome cases, the operation(s) at block 2310 may be performed during orafter the listen mode 2320.

During the CET period 2315, the first base station 2305-a may be in alisten mode 2320. While in the listen mode 2320, the first base station2305-a may receive at least one CET indicating timing information of atleast the second base station 2305-b over a shared spectrum. The atleast one CET may also indicate a timing stratum of at least the secondbase station 2305-b. The at least one CET may include a CET 2325 of thesecond base station 2305-b, which CET 2325 may be received during thetiming stratum-specific portion and the PLMN-specific portion identifiedat block 2310.

As shown, the first base station 2305-a may in some cases receive a CET2330 of a third base station or other base stations. The CET 2230 of thethird base station may be received concurrently with, or at a differenttime than, the CET 2325 of the second base station. The first basestation 2305-a may also transmit its own CET 2335 during its listen mode2320, which CET 2335 may indicate timing information of the first basestation 2305-a over the shared spectrum as well as a timing stratum ofthe first base station 2305-a.

At block 2340, a timing of the first base station 2305-a may be adjustedbased on the received timing information of at least the second basestation 2305-b. In some cases, the timing adjustment may includesynchronizing the timing of the first base station 2305-a to a timing ofat least the second base station 2305-b based on the received timinginformation. The timing of the first base station 2305-a may also besynchronized with other base stations, such as the third base station.

FIG. 24 is a message flow diagram 2400 illustrating wirelesscommunication between a first base station 2405-a and a second basestation 2405-b. The first base station 2405-a may in some cases beassociated with a higher timing stratum (e.g., TS2) than the timingstratum (e.g., TS1) of the second base station 2405-b. In some cases,the first base station 2405-a may be a member of a PLMN_A and the secondbase station 2405-b may be a member of a PLMN_B. The different PLMNs maybe synchronized with each other.

In some examples, each of the first base station 2405-a or the secondbase station 2405-b may be an example of one or more aspects of the basestation 105 or 205 described with reference to FIG. 1 or 2, or thedevice 1305 or 1405 described with reference to FIG. 13 or 14.

By way of example, the message flow may begin during a CET period 2410.During the CET period 2410, the first base station 2405-a may be in alisten mode 2415. While in the listen mode 2415, the first base station2405-a may receive at least one CET indicating timing information of atleast the second base station 2405-b over a shared spectrum. The atleast one CET may also indicate a timing stratum of at least the secondbase station 2405-b. The at least one CET may include a CET 2420 of thesecond base station 2405-b.

As shown, the first base station 2405-a may in some cases receive a CET2425 of a third base station or other base stations. The CET 2425 of thethird base station may be received concurrently with, or at a differenttime than, the CET 2420 of the second base station 2405-b. The firstbase station 2405-a may also transmit its own CET 2430 during its listenmode 2415, which CET 2430 may indicate timing information of the firstbase station 2405-a over the shared spectrum as well as a timing stratumof the first base station 2405-a.

At block 2435, a timing of the first base station 2405-a may be adjustedbased on the received timing information of at least the second basestation 2405-b. In some cases, the timing adjustment may includesynchronizing a timing of the first base station 2405-a to a timing ofat least the second base station 2405-b based on the received timinginformation. In this manner, the timing of a base station associatedwith one PLMN may be adjusted based on the timing of another basestation associated with another PLMN. The timing of the first basestation 2405-a may also be synchronized with other base stations, suchas the third base station.

FIG. 25 is a message flow diagram 2500 illustrating wirelesscommunication between a first base station 2505-a and a second basestation 2505-b. The first base station 2505-a may in some cases beassociated with a higher timing stratum (e.g., TS2) than the timingstratum (e.g., TS1) of the second base station 2505-b. In some cases,the first base station 2505-a and the second base station 2505-b may bemembers of a common PLMN. In other cases, the first base station 2505-aand the second base station 2505-b may be members of different PLMNsassociated with different operators. The different PLMNs may besynchronized with each other.

In some examples, each of the first base station 2505-a or the secondbase station 2505-b may be an example of one or more aspects of the basestation 105 or 205 described with reference to FIG. 1 or 2, or thedevice 1305, 1405, or 1605 described with reference to FIG. 13, 14, or16.

By way of example, the message flow may begin during a CET period 2510.During the CET period 2510, the first base station 2505-a may be in alisten mode 2515. While in the listen mode 2515, the first base station2505-a may receive at least one CET indicating timing information of atleast the second base station 2505-b over a shared spectrum. The atleast one CET may also indicate a timing stratum of at least the secondbase station 2505-b. The at least one CET may include a CET 2520 of thesecond base station 2505-b, which CET 2520 may be received during one ofa plurality of PLMN-specific regions of a CET period 2510 or during acommon transmission region 2525 of the CET period 2510. By way ofexample, the CET 2520 is shown to be received during the commontransmission region 2525.

As shown, the first base station 2505-a may in some cases receive a CET2530 of a third base station or other base stations. The CET 2530 of thethird base station may be received concurrently with, or at a differenttime than, the CET 2520 of the second base station 2505-b. The firstbase station 2505-a may also transmit its own CET 2535 during its listenmode 2515, which CET 2535 may indicate timing information of the firstbase station 2505-a over the shared spectrum as well as a timing stratumof the first base station 2505-a.

At block 2540, the first base station 2505-a may determine PLMNassignments of the PLMN-specific regions or common transmission region2525 of the CET period 2510. The determination may include adetermination of which PLMN-specific region is assigned to the PLMN ofthe second base station 2505-b, as well as a determination of whetherthe common transmission region 2525 is assigned to the PLMN of thesecond base station 2505-b. In some cases, it may be determined (e.g.,inferred) that the common transmission region 2525 is assigned to thePLMN of the second base station 2505-b based on an assignment of aPLMN-specific region having a particular time rank (e.g., the lastPLMN-specific region in time rank order) to the PLMN of the second basestation 2505-b for the particular CET period 2510. In some cases, theoperation(s) at block 2540 may be performed before or during the listenmode 2515.

At block 2545, a timing of the first base station 2505-a may be adjustedbased on the received timing information of at least the second basestation 2505-b. In some cases, the timing adjustment may includesynchronizing the timing of the first base station 2505-a to a timing ofat least the second base station 2505-b based on the received timinginformation. The timing of the first base station 2505-a may also besynchronized with other base stations, such as the third base station.

FIG. 26 is a message flow diagram 2600 illustrating wirelesscommunication between a first base station 2605-a and a second basestation 2605-b. The first base station 2605-a may in some cases beassociated with a higher timing stratum (e.g., TS2) than the timingstratum (e.g., TS1) of the second base station 2605-b. In some cases,the first base station 2605-a and the second base station 2605-b may bemembers of a common PLMN. In other cases, the first base station 2605-aand the second base station 2605-b may be members of different PLMNsassociated with different operators. The different PLMNs may besynchronized with each other.

In some examples, each of the first base station 2605-a or the secondbase station 2605-b may be an example of one or more aspects of the basestation 105 or 205 described with reference to FIG. 1 or 2, or thedevice 1305, 1405, or 1705 described with reference to FIG. 13, 14, or17.

By way of example, the message flow may begin during a CET period 2610.During the CET period 2610, the first base station 2605-a may be in alisten mode 2615. While in the listen mode 2615, the first base station2605-a may receive at least one CET indicating timing information of atleast the second base station 2605-b over a shared spectrum. The atleast one CET may also indicate a timing stratum of at least the secondbase station 2605-b. The at least one CET may include a CET 2620 of thesecond base station 2605-b, which CET 2620 may be received during one ofa plurality of PLMN-specific regions of a CET period 2610 or during acommon transmission region 2625 of the CET period 2610. By way ofexample, the CET 2620 is shown to be received during the commontransmission region 2625.

As shown, the first base station 2605-a may in some cases receive a CET2630 of a third base station or other base stations. The CET 2630 of thethird base station may be received concurrently with, or at a differenttime than, the CET 2620 of the second base station 2605-b. The firstbase station 2605-a may also transmit its own CET 2635 during its listenmode 2615, which CET 2635 may indicate timing information of the firstbase station 2605-a over the shared spectrum as well as a timing stratumof the first base station 2605-a.

At block 2640, the first base station 2605-a may determine PLMNassignments of the PLMN-specific regions or PLMN and timing stratumassignments of the common transmission region 2625 of the CET period2610. The determinations may include a determination of whichPLMN-specific region is assigned to the PLMN of the second base station2605-b, as well as a determination of whether the common transmissionregion 2625 is assigned to the timing stratum and PLMN of the secondbase station 2605-b. In some cases, it may be determined (e.g.,inferred) that the common transmission region 2625 is assigned to thePLMN of the second base station 2605-b based on an assignment of aPLMN-specific region having a particular time rank (e.g., the lastPLMN-specific region in time rank order) to the PLMN of the second basestation 2605-b for the particular CET period 2610.

At block 2645, the first base station 2605-a may determine that thesecond base station 2605-b includes a compatible timing stratumsynchronization source for the first base station 2605-a. In some cases,the second base station 2605-b may be determined to include a compatibletiming stratum synchronization source because the timing stratumassociated with the second base station 2605-b is a lower stratum thanthe timing stratum associated with the first base station 2605-a. Insome cases, the second base station 2605-b may be determined to includea compatible timing stratum synchronization source because the timingstratum associated with the second base station 2605-b is a next lowerstratum than the timing stratum associated with the first base station2605-a.

At block 2650, the second base station 2605-b may be selected as a basisfor adjusting the timing of the first base station 2605-a. The secondbase station 2605-b may be selected in response to the determination(s)made at block 2645.

In some cases, the operation(s) at block 2640 or block 2645 may beperformed before or during the listen mode 2615.

At block 2655, a timing of the first base station 2605-a may be adjustedbased on the received timing information of at least the second basestation 2605-b. In some cases, the timing adjustment may includesynchronizing the timing of the first base station 2605-a to a timing ofat least the second base station 2605-b based on the received timinginformation. The timing of the first base station 2605-a may also besynchronized with other base stations, such as the third base station.

FIG. 27 is a message flow diagram 2700 illustrating wirelesscommunication between a first base station 2705-a and a second basestation 2705-b. The first base station 2705-a may in some cases beassociated with a higher timing stratum (e.g., TS2) than the timingstratum (e.g., TS1) of the second base station 2705-b. In some cases,the first base station 2705-a and the second base station 2705-b may bemembers of a common PLMN. In other cases, the first base station 2705-aand the second base station 2705-b may be members of different PLMNsassociated with different operators. The different PLMNs may besynchronized with each other.

In some examples, each of the first base station 2705-a or the secondbase station 2705-b may be an example of one or more aspects of the basestation 105 or 205 described with reference to FIG. 1 or 2, or thedevice 1305, 1405, or 1805 described with reference to FIG. 13, 14, or18.

The message flow diagram 2700 presumes that the first base station2705-a and the second base station 2705-b share a periodic CET timing.Because of the shared CET timing, the transmission of a CET by the firstbase station 2705-a may interfere with the first base station's receiptof a CET of the second base station 2705-b (e.g., because the respectiveCETs may be received and transmitted concurrently).

By way of example, the message flow may begin at block 2710 with thefirst base station 2705-a accessing a periodic gating schedule todetermine whether a CET of the first base station 2705-a should be gated(i.e., not transmitted) during a next CET period 2720. The periodicgating schedule may indicate particular CET period(s) in which the CETof the first base station 2705-a should be gated to mitigateinterference with the first base station's receipt of a CET of at leastthe second base station 2705-b. At block 2715, it may be determined thatthe CET of the first base station 2705-a should be gated during the nextCET period 2720.

During the next CET period 2720, the first base station 2705-a may be ina listen mode 2725. While in the listen mode 2725, the first basestation 2705-a may receive at least one CET indicating timinginformation of at least the second base station 2705-b over a sharedspectrum. The at least one CET may also indicate a timing stratum of atleast the second base station 2705-b. The at least one CET may include aCET 2730 of the second base station 2705-b.

The first base station 2705-a may in some cases receive a CET of a thirdbase station or other base stations during the CET period 2720. The CETof the third base station may be received concurrently with, or at adifferent time than, the CET 2730 of the second base station 2705-b.

At block 2735, a timing of the first base station 2705-a may be adjustedbased on the received timing information of at least the second basestation 2705-b. In some cases, the timing adjustment may includesynchronizing a timing of the first base station 2705-a to a timing ofat least the second base station 2705-b based on the received timinginformation.

The timing of the first base station 2705-a may also be synchronizedwith other base stations, such as the third base station.

At block 2740, the first base station 2705-a may once again access theperiodic gating schedule to determine whether a CET of the first basestation 2705-a should be gated (i.e., not transmitted) during a next CETperiod 2750. At block 2745, it may be determined that the CET of thefirst base station 2705-a should be gated during the next CET period2750.

During the next CET period 2750, the first base station 2705-a may be ina listen mode 2755. While in the listen mode 2755, the first basestation 2705-a may receive at least one CET indicating timinginformation of at least the second base station 2705-b over a sharedspectrum. The at least one CET may also indicate a timing stratum of atleast the second base station 2705-b. The at least one CET may include aCET 2760 of the second base station 2705-b. Concurrent with its receiptof the CET 2760, the first base station 2705-a may transmit its own CET2765.

The first base station 2705-a may in some cases receive a CET of a thirdbase station or other base stations during the CET period 2750. The CETof the third base station may be received concurrently with, or at adifferent time than, the CET 2760 of the second base station 2705-b.

FIG. 28 is a message flow diagram 2800 illustrating wirelesscommunication between a first base station 2805-a and a second basestation 2805-b. The first base station 2805-a may in some cases beassociated with a higher timing stratum (e.g., TS2) than the timingstratum (e.g., TS1) of the second base station 2805-b. In some cases,the first base station 2805-a and the second base station 2805-b may bemembers of a common PLMN. In other cases, the first base station 2805-aand the second base station 2805-b may be members of different PLMNsassociated with different operators. The different PLMNs may besynchronized with each other.

In some examples, each of the first base station 2805-a or the secondbase station 2805-b may be an example of one or more aspects of the basestation 105 or 205 described with reference to FIG. 1 or 2, or thedevice 1305, 1905, 2005, or 2105 described with reference to FIG. 13,19, 20, or 21.

Prior to or during a CCA period 2810, the first base station 2805-a mayidentify a CCA slot 2840 for performing a CCA for the CCA period 2810,and the second base station 2805-b may identify a CCA slot 2820 forperforming a CCA for the CCA period 2810. The CCA slots 2840 and 2820may be identified based on the respective timing stratums of the firstand second base stations 2805-a, 2805-b, and may be used for purposes oftime or frequency synchronization over a shared spectrum. All basestations sharing a particular timing stratum may perform CCA in a CCAslot associated with the particular timing stratum.

By way of example, the message flow begins with the second base station2805-b performing its CCA, at block 2815, during the CCA slot 2820 ofthe CCA period 2810. Upon a successful CCA, the second base station2805-b may transmit timing information 2825, which timing information2825 may be received by the first base station 2805-a while in a listenmode 2830.

While in the listen mode 2830, the first base station 2805-a may performa CCA in a CCA slot 2840 of the CCA period 2810. However, because thesecond base station 2805-b successfully performed a CCA in CCA slot 2820of the CCA period 2810, before CCA was performed during the CCA slot2840, the CCA performed during the CCA slot 2840 may be unsuccessful.

At block 2845, a timing of the first base station 2805-a may be adjustedbased on the received timing information of at least the second basestation 2805-b. In some cases, the timing adjustment may includesynchronizing a timing of the first base station 2805-a to a timing ofat least the second base station 2805-b based on the received timinginformation. The timing of the first base station 2805-a may also besynchronized with other base stations, including base stations thatperform a CCA in the CCA slot 2820 or base stations that successfullyperform CCA and transmit timing information in other CCA periods.

FIG. 29 is a flow chart illustrating an example of a method 2900 ofwireless communication, in accordance with various aspects of thepresent disclosure. For clarity, the method 2900 is described below withreference to aspects of one or more of the base stations 105 or 205described with reference to FIG. 1, 2A, or 2B, or one of the devices1305, 1405, 1505, 1605, 1705, or 1805 described with reference to FIG.13, 14, 15, 16, 17, or 18. In some examples, a base station or devicesuch as one of the base stations 105 or 205 or one of the devices 1305,1405, 1505, 1605, 1705, or 1805 may execute one or more sets of codes tocontrol the functional elements of the device to perform the functionsdescribed below.

At block 2905, at least one CET may be received at a first base station.The at least one CET may indicate timing information of at least asecond base station over a shared spectrum. The at least one CET mayalso indicate a timing stratum of at least the second base station. Theoperation(s) at block 2905 may be performed by the timing managementmodule 1315, 1415, 1515, 1615, 1715, or 1815 described with reference toFIG. 13, 14, 15, 16, 17, or 18, or the CET timing information analysismodule 1425, 1525, 1625, 1725, or 1825 described with reference to FIG.14, 15, 16, 17, or 18.

At block 2910, a timing of the first base station may be adjusted basedon the received timing information of at least the second base station.The operation(s) at block 2910 may be performed by the timing managementmodule 1315, 1415, 1515, 1615, 1715, or 1815 described with reference toFIG. 13, 14, 15, 16, 17, or 18, or the timing adjustment module 1430,1530, 1630, 1730, or 1830 described with reference to FIG. 14, 15, 16,17, or 18.

In some examples, the at least one CET may be received during a CETperiod.

In some examples, the timing adjustment made at block 2910 may includesynchronizing a timing of the first base station to a timing of at leastthe second based station based on the received timing information.

In some examples, the at least one CET received at block 2905 mayinclude a first CET indicating the timing information of the second basestation over the shared spectrum and a second CET indicating timinginformation of a third base station over the shared spectrum. The firstCET and the second CET may be received at the first base stationconcurrently or at different times.

In some examples, the at least one CET may further indicate timinginformation for a third base station over the shared spectrum. In theseexamples, the timing of the first base station may in some cases beadjusted based on the timing information of the second base station andthe timing information of the third base station. More generally, thetiming of the first base station may be adjusted based on the timinginformation of any number of base stations.

In some cases, the first base station and the second base station may bemembers of a common PLMN. In other cases, the first base station and thesecond base station may be members of different PLMNs associated withdifferent operators. The different PLMNs may be synchronized with eachother.

In some examples, the first base station may transmit its own CET. TheCET of the first base station may indicate timing information of thefirst base station over the shared spectrum, as well as provide anindication of the timing stratum of the first base station.

In some examples, the at least one CET may be received during aparticular CET period of a plurality of periodically scheduled CETperiods. Each of the CET periods may include at least one PLMN-specificregion and a common transmission region. In some cases, the timinginformation of at least the second base station may be received duringthe common transmission region of the particular CET period, or a CET ofthe first base station may be transmitted during the common transmissionregion.

Thus, the method 2900 may provide for wireless communication. It shouldbe noted that the method 2900 is just one implementation and that theoperations of the method 2900 may be rearranged or otherwise modifiedsuch that other implementations are possible.

FIG. 30 is a flow chart illustrating an example of a method 3000 ofwireless communication, in accordance with various aspects of thepresent disclosure. For clarity, the method 3000 is described below withreference to aspects of one or more of the base stations 105 or 205described with reference to FIG. 1, 2A, or 2B, or one of the devices1305, 1405, or 1505 described with reference to FIG. 13, 14, or 15. Insome examples, a base station or device such as one of the base stations105 or 205 or one of the devices 1305, 1405, or 1505 may execute one ormore sets of codes to control the functional elements of the device toperform the functions described below.

The method 3000 presumes that CETs are transmitted or received during aCET period, as described with reference to FIG. 8. The CET period mayinclude a plurality of timing stratum-specific portions or a pluralityof PLMN-specific portions. When a CET period includes a plurality oftiming stratum-specific portions, each of the timing stratum-specificportions may be assigned to one of a plurality of timing stratums. Thetiming stratums may include a timing stratum associated with a secondbase station. When a CET period includes a plurality of PLMN-specificportions, each of the PLMN-specific portions may be assigned to one of aplurality of PLMNs. The plurality of PLMNs may include a PLMN associatedwith the second base station.

At block 3005, and for the CET period, a first base station may identifya timing stratum-specific portion associated with a timing stratum of asecond base station or a PLMN-specific portion associated with a PLMN ofthe second base station (i.e., both a timing stratum-specific portionassociated with the timing stratum of the second base station and aPLMN-specific portion associated with the PLMN of the second basestation, when both are available). The operation(s) at block 3005 may beperformed by the timing management module 1315, 1415, or 1515 describedwith reference to FIG. 13, 14, or 15, the CET timing informationanalysis module 1425 or 1525 described with reference to FIG. 14 or 15,or the CET period portion identification module 1540 described withreference to FIG. 15.

In some examples, the timing stratum-specific portion associated withthe timing stratum of the second base station or the PLMN-specificportion associated with the PLMN of the second base station may beidentified because the timing stratum associated with the second basestation is a lower stratum than the timing stratum associated with thefirst base station. In some cases, the timing stratum associated withthe second base station may be a next lower stratum than the timingstratum associated with the first base station.

At block 3010, at least one CET may be received at the first basestation. Each of the at least one CET may be received during a timingstratum-specific portion or a PLMN-specific portion of the CET period.The at least one CET may indicate timing information of at least thesecond base station over a shared spectrum. The at least one CET mayalso indicate a timing stratum of at least the second base station. Thetiming information of the second base station may be received bylistening to the identified timing stratum-specific portion or theidentified PLMN-specific portion (i.e., both the timing stratum-specificportion associated with the timing stratum of the second base stationand the PLMN-specific portion associated with the PLMN of the secondbase station, when both are available).

The operation(s) at block 3010 may be performed by the timing managementmodule 1315, 1415, or 1515 described with reference to FIG. 13, 14, or15, or the CET timing information analysis module 1425 or 1525 describedwith reference to FIG. 14 or 15.

At block 3015, a timing of the first base station may be adjusted basedon the received timing information of at least the second base station.The operation(s) at block 3015 may be performed by the timing managementmodule 1315, 1415, or 1515 described with reference to FIG. 13, 14, or15, or the timing adjustment module 1430 or 1530 described withreference to FIG. 14 or 15.

In some examples, the timing adjustment made at block 3015 may includesynchronizing a timing of the first base station to a timing of at leastthe second based station based on the received timing information.

In some examples, the at least one CET received at block 3010 mayinclude a first CET indicating the timing information of the second basestation over the shared spectrum and a second CET indicating timinginformation of a third base station over the shared spectrum. The firstCET and the second CET may be received at the first base stationconcurrently (e.g., in the same timing stratum-specific portion orPLMN-specific portion of a CET period (i.e., both the same timingstratum-specific portion and PLMN-specific portion, when both areavailable)) or at different times (e.g., in different timingstratum-specific portions or different PLMN-specific portions).

In some examples, the at least one CET may further indicate timinginformation for a third base station over the shared spectrum. In theseexamples, the timing of the first base station may in some cases beadjusted based on the timing information of the second base station andthe timing information of the third base station. More generally, thetiming of the first base station may be adjusted based on the timinginformation of any number of base stations.

In some examples, the first base station may transmit its own CET. TheCET of the first base station may indicate timing information of thefirst base station over the shared spectrum, as well as provide anindication of the timing stratum of the first base station.

Thus, the method 3000 may provide for wireless communication. It shouldbe noted that the method 3000 is just one implementation and that theoperations of the method 3000 may be rearranged or otherwise modifiedsuch that other implementations are possible.

FIG. 31 is a flow chart illustrating an example of a method 3100 ofwireless communication, in accordance with various aspects of thepresent disclosure. For clarity, the method 3100 is described below withreference to aspects of one or more of the base stations 105 or 205described with reference to FIG. 1, 2A, or 2B, or one of the devices1305, 1405, or 1605 described with reference to FIG. 13, 14, or 16. Insome examples, a base station or device such as one of the base stations105 or 205 or one of the devices 1305, 1405, or 1605 may execute one ormore sets of codes to control the functional elements of the device toperform the functions described below.

The method 3100 presumes that CETs are transmitted or received during aCET period. The CET period may be one of a plurality of periodicallyscheduled CET periods, in which each of the plurality of periodicallyscheduled CET periods may include a plurality of PLMN-specific regionsand a common transmission region, as described with reference to FIG.10. The PLMN-specific regions of each CET period may have a time rankorder, and PLMN-specific regions of different time rank may be assignedto different PLMNs in different CET periods. Likewise, the commontransmission regions of different CET periods may be assigned todifferent PLMNs in different CET periods. In some cases, thePLMN-specific regions or the common transmission regions may be assignedto different PLMNs in different CET periods on a rotating basis.

At block 3105, at least one CET may be received at a first base station.The at least one CET may be received during a particular CET period ofthe plurality of periodically scheduled CET periods. The at least oneCET may indicate timing information of at least a second base stationover a shared spectrum. The at least one CET may also indicate a timingstratum of at least the second base station. In some cases, the timinginformation of at least the second base station may be received duringone of the PLMN-specific regions. In other cases, the timing informationof at least the second base station may be received during the commontransmission region. The operation(s) at block 3105 may be performed bythe timing management module 1315, 1415, or 1615 described withreference to FIG. 13, 14, or 16, or the CET timing information analysismodule 1425 or 1625 described with reference to FIG. 14 or 16.

At block 3110, the PLMN assignments of the PLMN-specific regions orcommon transmission region may be determined for a particular CETperiod. The determination may include a determination of whichPLMN-specific region is assigned to the PLMN of the second base station,as well as a determination of whether the common transmission region isassigned to the PLMN of the second base station. In some cases, it maybe determined (e.g., inferred) that the common transmission region isassigned to the PLMN of the second base station based on an assignmentof a PLMN-specific region having a particular time rank (e.g., the lastPLMN-specific region in time rank order) to the PLMN of the second basestation for the particular CET period. The operation(s) at block 3110may be performed by the timing management module 1315, 1415, or 1615described with reference to FIG. 13, 14, or 16, the CET timinginformation analysis module 1425 or 1625 described with reference toFIG. 14 or 16, or the PLMN assignment determination module 1640described with reference to FIG. 16.

At block 3115, a timing of the first base station may be adjusted basedon the received timing information of at least the second base station.The operation(s) at block 3115 may be performed by the timing managementmodule 1315, 1415, or 1615 described with reference to FIG. 13, 14, or16, or the timing adjustment module 1430 or 1630 described withreference to FIG. 14 or 16.

In some examples, the timing adjustment made at block 3115 may includesynchronizing a timing of the first base station to a timing of at leastthe second based station based on the received timing information.

In some examples, the at least one CET received at block 3110 mayinclude a first CET indicating the timing information of the second basestation over the shared spectrum and a second CET indicating timinginformation of a third base station over the shared spectrum. The firstCET and the second CET may be received at the first base stationconcurrently or at different times.

In some examples, the at least one CET may further indicate timinginformation for a third base station over the shared spectrum. In theseexamples, the timing of the first base station may in some cases beadjusted based on the timing information of the second base station andthe timing information of the third base station. More generally, thetiming of the first base station may be adjusted based on the timinginformation of any number of base stations.

In some cases, the first base station and the second base station may bemembers of a common PLMN. In other cases, the first base station and thesecond base station may be members of different PLMNs associated withdifferent operators. The different PLMNs may be synchronized with eachother.

In some examples, the first base station may transmit its own CET. TheCET of the first base station may indicate timing information of thefirst base station over the shared spectrum, as well as provide anindication of the timing stratum of the first base station.

Thus, the method 3100 may provide for wireless communication. It shouldbe noted that the method 3100 is just one implementation and that theoperations of the method 3100 may be rearranged or otherwise modifiedsuch that other implementations are possible.

FIG. 32 is a flow chart illustrating an example of a method 3200 ofwireless communication, in accordance with various aspects of thepresent disclosure. For clarity, the method 3200 is described below withreference to aspects of one or more of the base stations 105 or 205described with reference to FIG. 1, 2A, or 2B, or one of the devices1305, 1405, or 1605 described with reference to FIG. 13, 14, or 17. Insome examples, a base station or device such as one of the base stations105 or 205 or one of the devices 1305, 1405, or 1705 may execute one ormore sets of codes to control the functional elements of the device toperform the functions described below.

The method 3200 presumes that CETs are transmitted or received during aCET period. The CET period may be one of a plurality of periodicallyscheduled CET periods, in which each of the plurality of periodicallyscheduled CET periods may include a plurality of PLMN-specific regionsand a common transmission region. The PLMN-specific regions of each CETperiod may have a time rank order, and PLMN-specific regions ofdifferent time rank may be assigned to different PLMNs in different CETperiods. The common transmission regions of different CET periods may beassigned to different combinations of

PLMNs and timing stratums in different CET periods. In some cases, thePLMN-specific regions may be assigned to different PLMNs in differentCET periods on a rotating basis. Likewise, the common transmissionregions may be assigned to different combinations of PLMNs and timingstratums in different CET periods on a rotating basis.

At block 3205, at least one CET may be received at a first base station.The at least one CET may be received during a particular CET period ofthe plurality of periodically scheduled CET periods. The at least oneCET may indicate timing information of at least a second base stationover a shared spectrum. The at least one CET may also indicate a timingstratum of at least the second base station. In some cases, the timinginformation of at least the second base station may be received duringone of the PLMN-specific regions. In other cases, the timing informationof at least the second base station may be received during the commontransmission region. The operation(s) at block 3205 may be performed bythe timing management module 1315, 1415, or 1715 described withreference to FIG. 13, 14, or 17, or the CET timing information analysismodule 1425 or 1725 described with reference to FIG. 14 or 17.

At block 3210, the PLMN assignments of the PLMN-specific regions or thePLMN and timing stratum assignments of the common transmission regionmay be determined for the particular CET period. The determination mayinclude a determination of which PLMN-specific region is assigned to thePLMN of the second base station, as well as a determination of whetherthe common transmission region is assigned to the PLMN and timingstratum of the second base station. In some cases, it may be determined(e.g., inferred) that the common transmission region is assigned to thePLMN of the second base station based on an assignment of aPLMN-specific region having a particular time rank (e.g., the lastPLMN-specific region in time rank order) to the PLMN of the second basestation for the particular CET period. The operation(s) at block 3210may be performed by the timing management module 1315, 1415, or 1715described with reference to FIG. 13, 14, or 17, the CET timinginformation analysis module 1425 or 1725 described with reference toFIG. 14 or 17, or the PLMN assignment determination module 1740described with reference to FIG. 17.

At block 3215, it may be determined that the second base stationincludes a compatible timing stratum synchronization source for thefirst base station. In some cases, the second base station may bedetermined to include a compatible timing stratum synchronization sourcebecause the timing stratum associated with the second base station is alower stratum than the timing stratum associated with the first basestation. In some cases, the second base station may be determined toinclude a compatible timing stratum synchronization source because thetiming stratum associated with the second base station is a next lowerstratum than the timing stratum associated with the first base station.

At block 3220, the second base station may be selected as a basis foradjusting the timing of the first base station. The second base stationmay be selected in response to the determination(s) made at block 3215.

The operation(s) at block 3215 or block 3220 may be performed by thetiming management module 1315, 1415, or 1715 described with reference toFIG. 13, 14, or 17, the CET timing information analysis module 1425 or1725 described with reference to FIG. 14 or 17, or the timing sourceselection module 1745 described with reference to FIG. 17.

At block 3225, a timing of the first base station may be adjusted basedon the received timing information of at least the second base station.The operation(s) at block 3225 may be performed by the timing managementmodule 1315, 1415, or 1715 described with reference to FIG. 13, 14, or17, or the timing adjustment module 1430 or 1730 described withreference to FIG. 14 or 17.

In some examples, the timing adjustment made at block 3225 may includesynchronizing a timing of the first base station to a timing of at leastthe second based station based on the received timing information.

In some examples, the at least one CET received at block 3205 mayinclude a first CET indicating the timing information of the second basestation over the shared spectrum and a second CET indicating timinginformation of a third base station over the shared spectrum. The firstCET and the second CET may be received at the first base stationconcurrently or at different times.

In some examples, the at least one CET may further indicate timinginformation for a third base station over the shared spectrum. In theseexamples, the timing of the first base station may in some cases beadjusted based on the timing information of the second base station andthe timing information of the third base station. More generally, thetiming of the first base station may be adjusted based on the timinginformation of any number of base stations.

In some cases, the first base station and the second base station may bemembers of a common PLMN. In other cases, the first base station and thesecond base station may be members of different PLMNs associated withdifferent operators. The different PLMNs may be synchronized with eachother.

In some examples, the first base station may transmit its own CET. TheCET of the first base station may indicate timing information of thefirst base station over the shared spectrum, as well as provide anindication of the timing stratum of the first base station.

Thus, the method 3200 may provide for wireless communication. It shouldbe noted that the method 3200 is just one implementation and that theoperations of the method 3200 may be rearranged or otherwise modifiedsuch that other implementations are possible.

FIG. 33 is a flow chart illustrating an example of a method 3300 ofwireless communication, in accordance with various aspects of thepresent disclosure. For clarity, the method 3300 is described below withreference to aspects of one or more of the base stations 105 or 205described with reference to FIG. 1, 2A, or 2B, or one of the devices1305, 1405, or 1805 described with reference to FIG. 13, 14, or 18. Insome examples, a base station or device such as one of the base stations105 or 205 or one of the devices 1305, 1405, or 1805 may execute one ormore sets of codes to control the functional elements of the device toperform the functions described below.

The method 3300 presumes that a first base station and at least a secondbase station share a periodic CET timing. Because of the shared CETtiming, the transmission of a CET by the first base station mayinterfere with the first base station's receipt of a CET of at least thesecond base station (e.g., because the respective CETs may be receivedand transmitted concurrently).

At block 3305, a periodic gating schedule may be accessed to determine,at block 3310, whether the CET of the first base station should be gated(i.e., not transmitted) in a next CET period. The periodic gatingschedule may indicate particular CET period(s) in which the CET of thefirst base station should be gated to mitigate interference with thefirst base station's receipt of the CET of at least the second basestation. When it is determined that the CET of the first base stationshould be gated in the current CET period, processing may proceed toblock 3315. When it is determined that the CET of the first base stationshould be transmitted in the current CET period, processing may proceedto block 3320. The operation(s) at block 3305 or 3310 may be performedby the timing management module 1315, 1415, or 1815 described withreference to FIG. 13, 14, or 18, the CET timing information analysismodule 1425 or 1825 described with reference to FIG. 14 or 18, or thegating module 1840 described with reference to FIG. 18.

At block 3315, at least one CET may be received at the first basestation while the first base station refrains from transmitting its ownCET. The at least one CET may indicate timing information of at leastthe second base station over a shared spectrum. The at least one CET mayalso indicate a timing stratum of at least the second base station. Theoperation(s) at block 3315 may be performed by the timing managementmodule 1315, 1415, or 1815 described with reference to FIG. 13, 14, or18, or the CET timing information analysis module 1425 or 1825 describedwith reference to FIG. 14 or 18.

At block 3320, a timing of the first base station may be adjusted basedon the received timing information of at least the second base station.The operation(s) at block 3320 may be performed by the timing managementmodule 1315, 1415, or 1815 described with reference to FIG. 13, 14, or18, or the timing adjustment module 1430 or 1830 described withreference to FIG. 14 or 18.

In some examples, the timing adjustment made at block 3320 may includesynchronizing a timing of the first base station to a timing of at leastthe second based station based on the received timing information.

At block 3325, a timing stratum of the first base station may bedetermined. The operation(s) at block 3325 may be performed by thetiming management module 1315, 1415, or 1815 described with reference toFIG. 13, 14, or 18, the CET timing information analysis module 1425 or1825 described with reference to FIG. 14 or 18, or the timing stratumdetermination module 1845 described with reference to FIG. 18.

At block 3330, at least one CET may be received at the first basestation while the first base station concurrently transmits its own CET.The at least one CET received at the first base station may indicatetiming information of at least a second base station over a sharedspectrum. The CET of the first base station may indicate timinginformation of the first base station over the shared spectrum and anindication of the timing stratum of the first base station. Theoperation(s) at block 3330 may be performed by the timing managementmodule 1315, 1415, or 1815 described with reference to FIG. 13, 14, or18, or the CET timing information analysis module 1425 or 1825 describedwith reference to FIG. 14 or 18.

In some examples, the at least one CET received at block 3315 mayinclude a first CET indicating the timing information of the second basestation over the shared spectrum and a second CET indicating timinginformation of a third base station over the shared spectrum. The firstCET and the second CET may be received at the first base stationconcurrently or at different times.

In some examples, the at least one CET may further indicate timinginformation for a third base station over the shared spectrum. In theseexamples, the timing of the first base station may in some cases beadjusted based on the timing information of the second base station andthe timing information of the third base station. More generally, thetiming of the first base station may be adjusted based on the timinginformation of any number of base stations.

In some cases, the first base station and the second base station may bemembers of a common PLMN. In other cases, the first base station and thesecond base station may be members of different PLMNs associated withdifferent operators. The different PLMNs may be synchronized with eachother.

In some examples, the at least one CET may be received during aparticular CET period of a plurality of periodically scheduled CETperiods. Each of the CET periods may include at least one PLMN-specificregion and a common transmission region. In some cases, the timinginformation of at least the second base station may be received duringthe common transmission region of the particular CET period or a CET ofthe first base station may be transmitted during the common transmissionregion.

Thus, the method 3300 may provide for wireless communication. It shouldbe noted that the method 3300 is just one implementation and that theoperations of the method 3300 may be rearranged or otherwise modifiedsuch that other implementations are possible.

FIG. 34 is a flow chart illustrating an example of a method 3400 ofwireless communication, in accordance with various aspects of thepresent disclosure. For clarity, the method 3400 is described below withreference to aspects of one or more of the base stations 105 or 205described with reference to FIG. 1, 2A, or 2B, or one of the devices1305, 1905, 2005, or 2105 described with reference to FIG. 13, 19, 20,or 21. In some examples, a base station or device such as one of thebase stations 105 or 205 or one of the devices 1305, 1905, 2005, or 2105may execute one or more sets of codes to control the functional elementsof the device to perform the functions described below.

At block 3405, a CCA slot assigned to a first base station for a frame(e.g., a synchronization frame) of a shared spectrum may be identified.The frame may be a frame associated with time synchronization, asdescribed, for example, with reference to FIG. 11. In some cases, theframe may be one of a plurality of periodic sync frames. Theoperation(s) at block 3405 may be performed by the timing managementmodule 1315, 1915, 2015, or 2115 described with reference to FIG. 13,19, 20, or 21, or the CCA slot identification module 1925, 2025, or 2125described with reference to FIG. 19, 20, or 21.

In some examples, the CCA slot assigned to the first base station in aframe of the shared spectrum may be identified based on a timing stratumof the first base station.

In some examples, the CCA slot assigned to the first base station mayoccur earlier in a frame than one or more CCA slots associated withtiming stratums that are higher than the timing stratum of the firstbase station (e.g., if the first base station is associated with a lowertiming stratum and is a GPS source, or is associated with a timingstratum that is closer to a GPS source in a synchronization stratum thanother base stations, the first base station may perform CCA in a CCAslot that occurs earlier in a frame than one or more other CCA slots).In general, base stations associated with lower timing stratums may beassigned CCA slots that occur earlier in a frame.

At block 3410, a CCA may be performed at the identified CCA slot for theframe. The operation(s) at block 3410 may be performed by the timingmanagement module 1315, 1915, 2015, or 2015 described with reference toFIG. 13, 19, 20, or 21, or the CCA module 1930, 2030, or 2130 describedwith reference to FIG. 19, 20, or 21.

At block 3415, and when the CCA is successful, a first timinginformation of the first base station may be selectively transmitted.The operation(s) at block 3415 may be performed by the timing managementmodule 1315, 1915, 2015, or 2115 described with reference to FIG. 13,19, 20, or 21, or the timing transmission module 1935, 2035, or 2135described with reference to FIG. 19, 20, or 21.

At block 3420, and when the CCA is unsuccessful, the first base stationmay listen for a second timing information of a second base stationduring the frame. The operation(s) at block 3420 may be performed by thetiming management module 1315, 1915, 2015, or 2115 described withreference to FIG. 13, 19, 20, or 21, or the timing reception module1940, 2040, or 2140 described with reference to FIG. 19, 20, or 21.

In some examples, and when the CCA is unsuccessful, the first basestation may further listen for a third timing information of a thirdbase station during the frame. The second timing information and thethird timing information may in some cases be received concurrently. Thefirst base station may also, and concurrently, listen for and receiveadditional timing information of additional base stations.

In some examples, a CCA frequency of the first base station may be gatedfor a plurality of frames associated with timing synchronization (i.e.,CCA may not be performed in certain timing synchronization frames). Aperiodicity of the gating may be based on the timing stratum of thefirst base stratum. In some cases, the CCAs of base stations associatedwith higher timing stratums may be gated more often than the CCAs ofbase stations associated with lower timing stratums. In some cases, theCCAs of base stations associated with a lowest timing stratum, such asGPS sources, may never be gated.

Thus, the method 3400 may provide for wireless communication. It shouldbe noted that the method 3400 is just one implementation and that theoperations of the method 3400 may be rearranged or otherwise modifiedsuch that other implementations are possible.

FIG. 35 is a flow chart illustrating an example of a method 3500 ofwireless communication, in accordance with various aspects of thepresent disclosure. For clarity, the method 3500 is described below withreference to aspects of one or more of the base stations 105 or 205described with reference to FIG. 1, 2A, or 2B, or one of the devices1305, 1905, or 2105 described with reference to FIG. 13, 19, or 21. Insome examples, a base station or device such as one of the base stations105 or 205 or one of the devices 1305, 1905, or 2105 may execute one ormore sets of codes to control the functional elements of the device toperform the functions described below.

In some examples, a CCA slot timing of the first base station may bedelayed based on a timing stratum of the first base station.

At block 3505, a CCA slot assigned to a first base station for a frame(e.g., a synchronization frame) of a shared spectrum may be identified.The frame may be a frame associated with time synchronization. In somecases, the frame may be one of a plurality of periodic sync frames. Insome cases, a timing of the CCA slot assigned to the first base stationmay be delayed with respect to a CCA period associated with a CCA slotassigned to a base station having a timing stratum that is lower than atiming stratum of the first base station, as described, for example,with reference to FIG. 12. The operation(s) at block 3505 may beperformed by the timing management module 1315, 1915, 2015, or 2115described with reference to FIG. 13, 19, 20, or 21, or the CCA slotidentification module 2025 described with reference to FIG. 20.

In some examples, the CCA slot assigned to the first base station in aframe of the shared spectrum may be identified based on a timing stratumof the first base station.

In some examples, the CCA slot assigned to the first base station mayoccur earlier in a frame than one or more CCA slots associated withtiming stratums that are higher than the timing stratum of the firstbase station (e.g., if the first base station is associated with a lowertiming stratum and is a GPS source, or is associated with a timingstratum that is closer to a GPS source in a synchronization stratum thanother base stations, the first base station may perform CCA in a CCAslot that occurs earlier in a frame than one or more other CCA slots).In general, base stations associated with lower timing stratums may beassigned CCA slots that occur earlier in a frame. However, when thefirst base station is associated with a higher stratum and the timing ofthe CCA slot assigned to the first base station is delayed with respectto a CCA period associated with a CCA slot assigned to a base stationhaving a lower timing stratum, the delay may enable the first basestation to gain access to the shared spectrum regardless of another basestation gaining access to the shared spectrum during an earlier part ofthe frame.

At block 3510, a CCA may be performed at the identified CCA slot for theframe. The operation(s) at block 3510 may be performed by the timingmanagement module 1315, 1915, 2015, or 2015 described with reference toFIG. 13, 19, 20, or 21, or the CCA module 1930, 2030, or 2130 describedwith reference to FIG. 19, 20, or 21.

At block 3515, and when the CCA is successful, a first timinginformation of the first base station may be selectively transmitted.The operation(s) at block 3515 may be performed by the timing managementmodule 1315, 1915, 2015, or 2115 described with reference to FIG. 13,19, 20, or 21, or the timing transmission module 1935, 2035, or 2135described with reference to FIG. 19, 20, or 21.

At block 3520, and when the CCA is unsuccessful, the first base stationmay listen for a second timing information of a second base stationduring the frame. The operation(s) at block 3520 may be performed by thetiming management module 1315, 1915, 2015, or 2115 described withreference to FIG. 13, 19, 20, or 21, or the timing reception module1940, 2040, or 2140 described with reference to FIG. 19, 20, or 21.

In some examples, and when the CCA is unsuccessful, the first basestation may further listen for a third timing information of a thirdbase station during the frame. The second timing information and thethird timing information may in some cases be received concurrently. Thefirst base station may also, and concurrently, listen for and receiveadditional timing information of additional base stations.

In some examples, a CCA frequency of the first base station may be gatedfor a plurality of frames associated with timing synchronization (i.e.,CCA may not be performed in certain timing synchronization frames). Aperiodicity of the gating may be based on the timing stratum of thefirst base stratum. In some cases, the CCAs of base stations associatedwith higher timing stratums may be gated more often than the CCAs ofbase stations associated with lower timing stratums. In some cases, theCCAs of base stations associated with a lowest timing stratum, such asGPS sources, may never be gated.

Thus, the method 3500 may provide for wireless communication. It shouldbe noted that the method 3500 is just one implementation and that theoperations of the method 3500 may be rearranged or otherwise modifiedsuch that other implementations are possible.

FIG. 36 is a flow chart illustrating an example of a method 3600 ofwireless communication, in accordance with various aspects of thepresent disclosure. For clarity, the method 3600 is described below withreference to aspects of one or more of the base stations 105 or 205described with reference to FIG. 1, 2A, or 2B, or one of the devices1305, 1905, 2005, or 2105 described with reference to FIG. 13, 19, 20,or 21. In some examples, a base station or device such as one of thebase stations 105 or 205 or one of the devices 1305, 1905, 2005, or 2105may execute one or more sets of codes to control the functional elementsof the device to perform the functions described below.

At block 3605, a CCA slot assigned to a first base station for a frameof a shared spectrum may be identified. The frame may be a frameassociated with time synchronization. The operation(s) at block 3605 maybe performed by the timing management module 1315, 1915, 2015, or 2115described with reference to FIG. 13, 19, 20, or 21, or the CCA slotidentification module 1925, 2025, or 2125 described with reference toFIG. 19, 20, or 21.

In some examples, the CCA slot assigned to the first base station in aframe of the shared spectrum may be identified based on a timing stratumof the first base station

In some examples, the CCA slot assigned to the first base station mayoccur earlier in a frame than one or more CCA slots associated withtiming stratums that are higher than the timing stratum of the firstbase station (e.g., if the first base station is associated with a lowertiming stratum and is a GPS source, or is associated with a timingstratum that is closer to a GPS source in a synchronization stratum thanother base stations, the first base station may perform CCA in a CCAslot that occurs earlier in a frame than one or more other CCA slots).In general, base stations associated with lower timing stratums may beassigned CCA slots that occur earlier in a frame.

At block 3610, a CCA may be performed at the identified CCA slot for theframe. The operation(s) at block 3610 may be performed by the timingmanagement module 1315, 1915, 2015, or 2015 described with reference toFIG. 13, 19, 20, or 21, or the CCA module 1930, 2030, or 2130 describedwith reference to FIG. 19, 20, or 21.

At block 3615, it may be determined whether the CCA performed at block3610 is successful. When the CCA is successful, processing may proceedto block 3620. When the CCA is unsuccessful, processing may proceed toblock 3630. The operation(s) at block 3615 may be performed by thetiming management module 1315, 1915, 2015, or 2015 described withreference to FIG. 13, 19, 20, or 21, or the CCA module 1930, 2030, or2130 described with reference to FIG. 19, 20, or 21.

At block 3620, a first timing information of the first base station maybe selectively transmitted. The first timing information may in somecases be transmitted during at least one reference signal resourceelement of the frame. The operation(s) at block 3620 may be performed bythe timing management module 1315, 1915, 2015, or 2115 described withreference to FIG. 13, 19, 20, or 21, or the timing transmission module1935, 2035, or 2135 described with reference to FIG. 19, 20, or 21.

At block 3625, the first base station may transmit data to at least oneUE during the frame. The data may in some cases be transmitted to the atleast one UE concurrent with the transmission of the first timinginformation at block 3620. The operation(s) at block 3620 may beperformed by the timing management module 1315, 1915, 2015, or 2115described with reference to FIG. 13, 19, 20, or 21, or the datatransmission module 2145 described with reference to FIG. 21.

At block 3630, and while listening for a second timing information of asecond base station during the frame, the first base station may receivea channel usage beacon signal from the second base station. Until thechannel usage beacon signal is received, the method 3600 may loop atblock 3630. Upon receipt of the channel usage beacon signal, the method3600 may proceed to block 3635. The operation(s) at block 3420 may beperformed by the timing management module 1315, 1915, 2015, or 2115described with reference to FIG. 13, 19, 20, or 21, or the timingreception module 1940, 2040, or 2140 described with reference to FIG.19, 20, or 21.

At block 3635, the second timing information may be received from thesecond base station during the frame, and at block 3640, a timing of thefirst base station may be adjusted based on the second timinginformation. In some cases, the timing of the first base station mayalso be adjusted based on a third timing information received from athird base station, or on timing information received from any number ofbase stations. The timing information received from the third basestation may be received during the same or a different frame in whichthe second timing information is received. The operation(s) at block3635 or block 3640 may be performed by the timing management module1315, 1915, 2015, or 2115 described with reference to FIG. 13, 19, 20,or 21, or the timing reception module 1940, 2040, or 2140 described withreference to FIG. 19, 20, or 21. The operation(s) at block 3640 may alsobe performed by the timing adjustment module 2150 described withreference to FIG. 21.

In some examples, a timing of the second base station may be determinedbased on the second timing information, and the timing of the first basestation may be adjusted by synchronizing the timing of the first basestation to the timing of the second base station.

In some examples, a CCA frequency of the first base station may be gatedfor a plurality of frames associated with timing synchronization (i.e.,CCA may not be performed in certain timing synchronization frames). Aperiodicity of the gating may be based on the timing stratum of thefirst base stratum. In some cases, the CCAs of base stations associatedwith higher timing stratums may be gated more often than the CCAs ofbase stations associated with lower timing stratums. In some cases, theCCAs of base stations associated with a lowest timing stratum, such asGPS sources, may never be gated.

Thus, the method 3600 may provide for wireless communication. It shouldbe noted that the method 3600 is just one implementation and that theoperations of the method 3600 may be rearranged or otherwise modifiedsuch that other implementations are possible.

In some cases, one or more aspects of the method 2900, 3000, 3100, 3200,3300, 3400, 3500, or 3600 described in FIG. 29, 30, 31, 32, 33, 34, 35,or 36 may be combined.

In addition to time synchronizing base stations, base stations may needto be frequency synchronized. However, in the case of base stationscommunicating over a shared spectrum, there may be no master basestation. Furthermore, the deployment of base stations may be ad-hoc,with no predefined physical placement or arrangement of base stations.Still further, there may be scenarios where a GPS source or backhaulconnection to a trusted synchronization source may be unavailable,requiring an ability to frequency synchronize a set of base stations inthe absence of such a source.

When frequency synchronizing a set of N access points (e.g., basestations), a frequency control loop may be created to maintain overallfrequency synchronization across the N access points. During thefrequency synchronization process, an access point may have disjointstate information. In other words, an access point may know its ownstate information and may acquire state information from nearby accesspoints, but because state information may not be routed through thenetwork, an access point may not have state information for more distantaccess points.

A given access point (AP_(i)) may have the ability to receive frequencyinformation from another local AP_(j) and measure a frequency errorΔf_(ij) between its own frequency oscillator and that of AP_(j). For aset of APs that are within reception of AP_(i), a set of Δf_(ij) may bemeasured for the set of j APs. These frequency errors may be used toestimate the relative frequency estimates of neighboring APs such thatAP_(i)'s estimate of AP_(j)'s frequency is given by:f _(j) =f _(i) +Δf _(ij)Where f_(i) is AP_(i)'s local oscillator (LO) frequency offset andΔf_(ij) is the AP_(i)'s measurement of the relative error between its LOand AP_(j)'s LO frequency. For simplicity, it may be assumed that themeasurement is noise free and that AP_(i)'s estimate of AP_(j) equalsthe true frequency of AP_(j). This restriction may be relaxed in someexamples. Given these frequency estimates as input, an AP can formulatea revision to its own frequency oscillator in an attempt to synchronizeits frequency with that of its local neighbor APs.

FIG. 37 illustrates an example network 3700 of N=3 deployed APs. For thecase of N=3, each of the three APs may use the frequency estimates ofthe other two APs to formulate an adjustment in its own frequency.

An equivalent set of recursion functions may be created for the examplenetwork 3700:f _(1,n+1) =t ₁₁ f _(1,n) +t ₁₂ f _(2,n) +t ₁₃ f _(3,n)f _(2,n+1) =t ₂₁ f _(1,n) +t ₂₂ f _(2,n) +t ₂₃ f _(3,n)f _(3,n+1) =t ₃₁ f _(1,n) +t ₃₃ f _(3,n)Where n is the iteration number and t_(ij) equals the coefficientmultiplier used by AP_(i) on the estimate of AP_(j). Equivalently, inmatrix formulation:f _(n+1) =T·f _(n)

For the case where each AP is limited to averaging of the inputfrequencies, each row of matrix T may sum to 1 and by definition is astochastic matrix. Some useful properties of stochastic matrices may bethe following:

-   -   All stochastic matrices have at least one maximum absolute        eigenvalue of λ=1.    -   For the case where T has a single eigenvalue occurrence of |λ|=1        then as n→∞, f_(n) approaches the eigenvector corresponding to        λ.    -   Convergence rate of elements of f are bounded by |λ₂|^(n) where        λ₂ is the subdominant eigenvalue denoting the second largest        eigenvalue in absolute magnitude.

For the example network 3700 of N=3, four cases may be considered toillustrate four distinct scenarios where analysis can be done in closedform.

FIG. 38 illustrates an example network 3800 of N=3 deployed APs. The APsare fully connected, with each AP having the ability to receive from theother two APs. Each AP may measure the frequency error at time n; form adirect average of the three frequencies; and apply that frequency to itsown LO at time n+1.

Direct averaging of the received signals may be applied to form thefollowing relation:

$f_{n + 1} = {{T \cdot f_{n}} = {\begin{bmatrix}{1/3} & {1/3} & {1/3} \\{1/3} & {1/3} & {1/3} \\{1/3} & {1/3} & {1/3}\end{bmatrix}f_{n}}}$

Where T is the transition probability matrix. Given that the rows of Tare guaranteed to sum to 1, T is a stochastic matrix with the uniqueproperty that at least one eigenvalue of T equals 1 and the absolutevalue of all of the other eigenvalues are less than or equal to 1.Additionally, the convergence rate over time will be determined by themagnitude of the second largest absolute valued eigenvalue and steadystate frequency will converge to a scalar multiple of the eigenvectorcorresponding to the largest absolute eigenvalue of 1, which in thiscase is [1 1 1]^(T). For the case of a stochastic matrix, this will bethe vector containing all elements identical to each other.

For this particular case, the eigenvalues are 1, 0, 0 with (approximate)eigenvectors of [0.5774, 0.5774, 0.5774]. Steady state is reached afterone iteration, or equivalently stated, T=T²=T³= . . . =T^(∞). Thisimmediate convergence results from the fact that the second largesteigenvalue is equal to 0. No change in matrix f occurs with any repeatedapplication of matrix T. The final solution therefore has all threefrequencies converged to a single average value vector that is a scalarmultiple of the eigenvector corresponding to the largest eigenvalue.

FIG. 39 illustrates an example network 3900 of N=3 deployed APs, wherethe three APs are deployed in a single line formation, with AP 1 and AP3 connected to different sides of AP 2.

Direct averaging of the received signals may be applied to form thefollowing relation:

$f_{n + 1} = {{T \cdot f_{n}} = {\begin{bmatrix}{1/2} & {1/2} & 0 \\{1/3} & {1/3} & {1/3} \\0 & {1/2} & {1/2}\end{bmatrix}f_{n}}}$

In the above matrix, the entries per row sum to 1 and have valuesdependent on each AP's number of local connections. The matrix T in thiscase is a tridiagonal stochastic matrix with eigenvalues of 1, 0.5,−0.1667. As in the case described with reference to FIG. 38, thefrequency converges to a steady state value of f=k·[1 1 1]^(T). However,for this case, convergence is not immediate. As long as the initialfrequency state f₀≠k·[1 1 1]^(T), the rate of convergence will bebounded by λ₂ ^(n)=(0.5)^(n).

One may compute the combining weights at steady state to determine theproportion of each AP's frequency contribution to the final equilibriumfrequency. This is equal to the top row vector of T^(∞). For the case ofthe 3×3 T matrix above, the proportion for each node is 28.6%, 42.9% and28.6%, for APs 1, 2, and 3, respectively. A general statement that canbe made is that APs that have a larger number of connections to otherAPs will contribute a greater proportion to the final equilibriumfrequency.

The case of APs being deployed in a single line formation should depictthe worst case convergence rates due to its lack of interconnectedness.Frequency information from an AP on one side of the network needs to becommunicated through all of the other APs to reach the other side of thenetwork. One can compute the subdominant eigenvalue for thisconfiguration for varying N and show that λ₂=0.5, 0.91, and 0.99 forN=3, 7, and 19, respectively. These large values of λ₂ for large valuesof N will result in slow convergence of the LO oscillators across thenetwork.

FIG. 40 illustrates another example network 4000 of N=3 deployed APs.However, there are asymmetric signal connections between the APs of theexample network 4000.

A recursion equation for the example network 4000 may be given by:

$f_{n + 1} = {{T \cdot f_{n}} = {\begin{bmatrix}0 & 0 & 1 \\1 & 0 & 0 \\0 & 1 & 0\end{bmatrix}f_{n}}}$

For this case, the frequency estimates are transferred from AP to AP ina ring with no direct symmetry of transfer between any pair of APs.While the matrix is stochastic, it is no longer symmetric, therebyresulting in complex eigenvalues. As a result, there is no convergenceof (T)^(∞). This results from the fact that there are multipleeigenvalues with an absolute value of 1. In this particular case, theeigenvalues are 1, −0.5+j*0.866, −0.5-j*0.866, which all have absolutevalue of 1. Steady state convergence of frequency will only result ifall APs have the same LO frequency, implying that the initial f₀ vectoris a scalar multiple of the eigenvector [1 1 1] corresponding to thelargest absolute eigenvalue of λ₁=1. For all other initial conditions,there will be continuous frequency oscillations for each AP in thenetwork.

FIG. 41 illustrates an example disjoint network 4100 of N=3 deployedAPs. However, there are asymmetric signal connections between the APs ofthe example network 4000.

A recursion equation for the example network 4000 may be given by:

$f_{n + 1} = {{T \cdot f_{n}} = {\begin{bmatrix}{1/2} & {1/2} & 0 \\{1/2} & {1/2} & 0 \\0 & 0 & 1\end{bmatrix}f_{n}}}$Or more generally:

$T = \begin{bmatrix}B_{k \times k} & \; & 0 \\\; & B_{l \times l} & \; \\0 & \; & B_{m \times m}\end{bmatrix}$Where k+1+m=N.

This is a degenerate case where T has the form of a diagonal blockmatrix, with each block B being a stochastic matrix. For the 3×3 matrixabove, the eigenvalues are 1, 1, 0. The repeated occurrence of λ=1implies that the network is disjoint. This generally applies to any Tmatrix that can be put into this diagonal block form by swapping anynumber of pairs of rows with each other. The number of eigenvalues withλ=1 will equal the number of blocks B.

In all of the cases described with reference to FIGS. 38-41, and for allstochastic T matrices in general, frequency stability across the networkmay be guaranteed when perfect information is assumed. For larger valuesof N, simulation is required to evaluate the convergence properties ofthe network. A reasonable model of an AP deployment along withspecification of pairwise connections is required. A probabilistic modelmay be created to specify these connections, and to try to reasonablytake into account the proximity of the APs with one another.

FIG. 42 illustrates an example network 4200 of 45 APs (e.g., APs 4205,4210, etc.). The APs may be divided into nine groups of five (Group 1,Group 2, . . . Group 9). These numbered groups are shown with an examplerelative placement of APs within each group. Amongst the five APs withina group, their pairwise probability of being bidirectionally connectedis given by probability P_(wg) and depicted with a line having noarrows. Additionally, across two sets of adjacent groups, a connectionmay be made between APs with a pairwise probability of P_(g) anddepicted with a line having at least one arrow. Additionally, thisgroup-to-group connection is allowed to be unidirectional orbidirectional based on the probability of being unidirectional, P_(u).Note that as P_(wg) and P_(g) values that approach the value of 1 andP_(u)=0, the network will become fully and bidirectionally connectedacross all 45 APs.

Thousands of 45×45 dimensioned matrices T may be created in simulationbased on the example network 4200 shown in FIG. 42, in order to analyzethe frequency convergence properties of the network 4200. Assuming firstthat P_(u)=0, the T matrix becomes stochastic and symmetric, where allrow entries sum to 1 and t_(ij)=t_(j), representing bidirectionalconnections between APs. Assuming that p_(wg)>p_(g), the matrix will bemore populated with nonzero elements towards the main diagonal. Towardthe off-diagonal portions of the matrix there will be non-zero entriespossible where one group is collated with another. For entriescorresponding to groups that are not collocated, the value of 0 isplaced.

Taking 5000 of these T matrices, statistics may be collected of thesecond largest eigenvalue in absolute magnitude. This distribution givesan idea of the convergence rate of the LO frequencies across thenetwork. The higher the magnitude, the longer the convergence timerequired.

The equations used in FIGS. 37-41 may be modified as disclosed below toinclude

Additive White Gaussian Noise (AWGN) terms that indicate the measurementerror that AP_(i) makes when estimating AP_(j)'s frequency offset:f _(1,n+1) =t ₁₁ f _(1,n) +t ₁₂ f _(2,n) +n ₁₂ +n ₁₃f _(2,n+1) =t ₂₁ t _(1,n) +n ₂₁ +t ₂₂ f _(2,n) +t ₂₃ f _(3,n) +n ₂₃f _(3,n+1) =t ₃₁ f _(1,n) +n ₃₁ +t ₃₂ f _(2,n) +n ₃₂ +t ₃₃ f _(3,n)

Where n_(ij) is the noise introduced in AP_(i)'s frequency estimate ofAP_(j). While the noise will vary based on the AP_(j) frequency that isestimated, the analysis may be simplified by using a single noise termper AP. For large N, this should be a reasonable assumption, andtherefore the recursion equation simplifies to:f _(n+1) =T·f _(n) +n _(n)

Where n_(n) is a noise vector of AWGN random variables with standarddeviation σ. Entries for each vector vary across both APs as well astime.

FIG. 43 shows a block diagram 4300 of a device 4305 for use in wirelesscommunication in a network including a plurality of device configured tocommunicate data over an unlicensed spectrum, in accordance with variousaspects of the present disclosure. In some examples, the device 4305 maybe an example of one or more aspects of one of the base stations 105 or205 described with reference to FIG. 1, 2A, or 2B. The device 4305 mayalso be a processor. The device 4305 may include a receiver module 4310,a frequency management module 4315, and a transmitter module 4320. Eachof these components may be in communication with each other.

The components of the device 4305 may, individually or collectively, beimplemented using one or more application-specific integrated circuits(ASICs) adapted to perform some or all of the applicable functions inhardware. Alternatively, the functions may be performed by one or moreother processing units (or cores), on one or more integrated circuits.In other examples, other types of integrated circuits may be used (e.g.,Structured/Platform ASICs, Field Programmable Gate Arrays (FPGAs), andother Semi-Custom ICs), which may be programmed in any manner known inthe art. The functions of each unit may also be implemented, in whole orin part, with instructions embodied in a memory, formatted to beexecuted by one or more general or application-specific processors.

In some examples, the receiver module 4310 may be or include a radiofrequency (RF) receiver, such as an RF receiver operable to receivetransmissions in a first spectrum (e.g., a licensed LTE spectrum) or asecond spectrum (e.g., a “shared spectrum” used by devices operatingunder different transmission protocols, such as an unlicensed spectrum).The receiver module 4310 may be used to receive various types of data orcontrol signals (i.e., transmissions) over one or more communicationlinks of a wireless communications system including the first and secondspectrums, such as one or more communication links of the wirelesscommunications system 100, 200, or 250 described with reference to FIG.1, 2A, or 2B.

In some examples, the transmitter module 4320 may be or include an RFtransmitter, such as an RF transmitter operable to transmit in the firstspectrum or the second spectrum. The transmitter module 4320 may be usedto transmit various types of data or control signals (i.e.,transmissions) over one or more communication links of the wirelesscommunications system including the first spectrum and the secondspectrum.

In some examples, the frequency management module 4315 may receivefrequency information from at least one neighboring device (e.g., atleast one neighboring base station) over an unlicensed spectrum. Thefrequency management module 4315 may use the received frequencyinformation to iteratively adjust the frequency of the device 4305.

FIG. 44 shows a block diagram 4400 of a device 4405 for use in wirelesscommunication in a network including a plurality of device configured tocommunicate data over an unlicensed spectrum, in accordance with variousaspects of the present disclosure. In some examples, the device 4405 maybe an example of one or more aspects of one of the base stations 105 or205 described with reference to FIG. 1 or 2, or the device 4305described with reference to FIG. 43. The device 4405 may also be aprocessor. The device 4405 may include a receiver module 4410, afrequency management module 4415, and a transmitter module 4420. Each ofthese components may be in communication with each other.

The components of the device 4405 may, individually or collectively, beimplemented using one or more ASICs adapted to perform some or all ofthe applicable functions in hardware. Alternatively, the functions maybe performed by one or more other processing units (or cores), on one ormore integrated circuits. In other examples, other types of integratedcircuits may be used (e.g., Structured/Platform ASICs, FPGAs, and otherSemi-Custom ICs), which may be programmed in any manner known in theart. The functions of each unit may also be implemented, in whole or inpart, with instructions embodied in a memory, formatted to be executedby one or more general or application-specific processors.

In some examples, the receiver module 4410 may be or include an RFreceiver, such as an RF receiver operable to receive transmissions in afirst spectrum (e.g., a licensed LTE spectrum) or a second spectrum(e.g., a “shared spectrum” used by devices operating under differenttransmission protocols, such as an unlicensed spectrum). The RF receivermay include separate receivers for the first spectrum and the secondspectrum. The separate receivers may in some cases take the form of alicensed spectrum receiver module 4412 for communicating over the firstspectrum, and an unlicensed spectrum receiver module 4414 forcommunicating over the second spectrum. The receiver module 4410,including the licensed spectrum receiver module 4412 or the unlicensedspectrum receiver module 4414, may be used to receive various types ofdata or control signals (i.e., transmissions) over one or morecommunication links of a wireless communications system including thelicensed and unlicensed spectrums, such as one or more communicationlinks of the wireless communications system 100, 200, or 250 describedwith reference to FIG. 1, 2A, or 2B.

In some examples, the transmitter module 4420 may be or include an RFtransmitter, such as an RF transmitter operable to transmit in the firstspectrum or the second spectrum. The RF transmitter may include separatetransmitters for the first spectrum and the second spectrum. Theseparate transmitters may in some cases take the form of a licensedspectrum transmitter module 4422 for communicating over the firstspectrum, and an unlicensed spectrum transmitter module 4424 forcommunicating over the second spectrum. The transmitter module 4420,including the licensed spectrum transmitter module 4422 or theunlicensed spectrum transmitter module 4424, may be used to transmitvarious types of data or control signals (i.e., transmissions) over oneor more communication links of the wireless communications systemincluding the licensed spectrum and the unlicensed spectrum.

In some examples, the frequency management module 4415 may be an exampleof one or more aspects of the frequency management module 4315 describedwith reference to FIG. 43 and may include a frequency informationanalysis module 4425, a coefficient multiplier generation module 4430,or a frequency adjustment module 4435.

In some examples, the frequency information analysis module 4425 may beused to receive frequency information from at least one neighboringdevice (e.g., at least one neighboring base station) of the network. Insome cases, the frequency information may be received from the at leastone neighboring device of the network during a periodic CET, such as oneof the CETs described with reference to FIG. 7, 8, 9, 10, 13, 14, 15,16, 17, 18, 22, 23, 24, 25, 26, 27, 29, 30, 31, or 32. In other cases,the frequency information may be received from the at least oneneighboring device of the network during a periodic frame associatedwith time synchronization, such as one of the CCAs described withreference to FIG. 11, 12, 13, 19, 20, 21, 28, 34, 35, or 36.

In some examples, the coefficient multiplier generation module 4430 maybe used to generate a plurality of coefficient multipliers including aseparate coefficient multiplier for the device 4405 and each of the atleast one neighboring device. The coefficient multipliers may be basedat least in part on a quantity of the at least one neighboring device.The plurality of coefficient multipliers may define a stochastic matrix.

In some examples, the coefficient multipliers may be held constant for aplurality (i.e., two or more) of recursive iterations through theoperations of the frequency information analysis module 4425, thecoefficient multiplier generation module 4430, or the frequencyadjustment module 4435. Holding the coefficient multipliers throughmultiple recursive iterations can increase the stability of frequencyadjustments and frequency convergence (e.g., frequency convergence amongthe device 4405 and the at least one neighboring device).

In some examples, the frequency adjustment module 4435 may adjust afrequency of the device 4405 based on the received frequency informationand the coefficient multipliers. The frequency adjustment may includesynchronizing a frequency of the device 4405 to a frequency of anunlicensed network over which the device 4405 and the at least oneneighboring device communicate.

FIG. 45 shows a block diagram 4500 of a device 4505 for use in wirelesscommunication in a network including a plurality of device configured tocommunicate data over an unlicensed spectrum, in accordance with variousaspects of the present disclosure. In some examples, the device 4505 maybe an example of one or more aspects of one of the base stations 105 or205 described with reference to FIG. 1 or 2, or the device 4305described with reference to FIG. 43. The device 4505 may also be aprocessor. The device 4505 may include a receiver module 4510, afrequency management module 4515, and a transmitter module 4520. Each ofthese components may be in communication with each other.

The components of the device 4505 may, individually or collectively, beimplemented using one or more ASICs adapted to perform some or all ofthe applicable functions in hardware. Alternatively, the functions maybe performed by one or more other processing units (or cores), on one ormore integrated circuits. In other examples, other types of integratedcircuits may be used (e.g., Structured/Platform ASICs, FPGAs, and otherSemi-Custom ICs), which may be programmed in any manner known in theart. The functions of each unit may also be implemented, in whole or inpart, with instructions embodied in a memory, formatted to be executedby one or more general or application-specific processors.

In some examples, the receiver module 4510 may be or include an RFreceiver, such as an RF receiver operable to receive transmissions in afirst spectrum (e.g., a licensed LTE spectrum) or a second spectrum(e.g., a “shared spectrum” used by devices operating under differenttransmission protocols, such as an unlicensed spectrum). The RF receivermay include separate receivers for the first spectrum and the secondspectrum. The separate receivers may in some cases take the form of alicensed spectrum receiver module 4512 for communicating over the firstspectrum, and an unlicensed spectrum receiver module 4514 forcommunicating over the second spectrum. The receiver module 4510,including the licensed spectrum receiver module 4512 or the unlicensedspectrum receiver module 4514, may be used to receive various types ofdata or control signals (i.e., transmissions) over one or morecommunication links of a wireless communications system including thelicensed and unlicensed spectrums, such as one or more communicationlinks of the wireless communications system 100, 200, or 250 describedwith reference to FIG. 1, 2A, or 2B.

In some examples, the transmitter module 4520 may be or include an RFtransmitter, such as an RF transmitter operable to transmit in the firstspectrum or the second spectrum. The RF transmitter may include separatetransmitters for the first spectrum and the second spectrum. Theseparate transmitters may in some cases take the form of a licensedspectrum transmitter module 4522 for communicating over the firstspectrum, and an unlicensed spectrum transmitter module 4524 forcommunicating over the second spectrum.

The transmitter module 4520, including the licensed spectrum transmittermodule 4522 or the unlicensed spectrum transmitter module 4524, may beused to transmit various types of data or control signals (i.e.,transmissions) over one or more communication links of the wirelesscommunications system including the licensed spectrum and the unlicensedspectrum.

In some examples, the frequency management module 4515 may be an exampleof one or more aspects of the frequency management module 4315 or 4415described with reference to FIG. 43 or 44 and may include a frequencyinformation analysis module 4525, a timing stratum determination module4530, a link quality determination module 4335, a coefficient multipliergeneration module 4540, or a frequency adjustment module 4545.

In some examples, the frequency information analysis module 4525 may beused to receive frequency information from at least one neighboringdevice (e.g., at least one neighboring base station) of the network. Insome cases, the frequency information may be received from the at leastone neighboring device of the network during a periodic CET, such as oneof the CETs described with reference to FIG. 7, 8, 9, 10, 13, 14, 15,16, 17, 18, 22, 23, 24, 25, 26, 27, 29, 30, 31, or 32. In other cases,the frequency information may be received from the at least oneneighboring device of the network during a periodic frame associatedwith time synchronization, such as one of the CCAs described withreference to FIG. 11, 12, 13, 19, 20, 21, 28, 34, 35, or 36.

In some examples, the timing stratum determination module 4530 may beused to determine a timing stratum of each of the at least oneneighboring device. By way of example, the timing stratum may bedetermined from the received frequency information or from informationreceived in one or more messages over the unlicensed spectrum or anotherspectrum (e.g., an LTE spectrum).

In some examples, the link quality determination module 4535 may be usedto a determine a link quality of each of the at least one neighboringdevice. By way of example, the link quality may be determined from thereceived frequency information.

In some examples, the coefficient multiplier generation module 4540 maybe used to generate a plurality of coefficient multipliers including aseparate coefficient multiplier for the device 4505 and each of the atleast one neighboring device. The coefficient multipliers may be basedat least in part on a quantity of the at least one neighboring device.The coefficient multiplier generated for each of the at least oneneighboring base station may be further based on the timing stratumassociated with that neighboring base station (e.g., to give higherweight to a base station associated with a lower stratum, such as a GPSsource (which in some cases may be assigned a coefficient multiplier ofone)). The coefficient multiplier generated for each of the at least oneneighboring base station may be further based on the link qualityassociated with that neighboring base station (e.g., to give higherweight to better link qualities). The plurality of coefficientmultipliers may define a stochastic matrix.

In some examples, the coefficient multipliers may be held constant for aplurality (i.e., two or more) of recursive iterations through theoperations of the frequency information analysis module 4525, the timingstratum determination module 4530, the link quality determination module4535, the coefficient multiplier generation module 4540, or thefrequency adjustment module 4545. Holding the coefficient multipliersthrough multiple recursive iterations can increase the stability offrequency adjustments and frequency convergence (e.g., frequencyconvergence among the device 4505 and the at least one neighboringdevice).

In some examples, the frequency adjustment module 4545 may adjust afrequency of the device 4505 based on the received frequency informationand the coefficient multipliers. The frequency adjustment may includesynchronizing a frequency of the device 4505 to a frequency of anunlicensed network over which the device 4505 and the at least oneneighboring device communicate.

FIG. 46 is a flow chart illustrating an example of a method 4600 ofwireless communication in a network including a plurality of basestations configured to communicate data over an unlicensed spectrum, inaccordance with various aspects of the present disclosure. For clarity,the method4600 is described below with reference to aspects of one ormore of the base stations 105 or 205 described with reference to FIG. 1,2A, or 2B, or one of the devices 4305, 4405, or 4505 described withreference to FIG. 43, 44, or 45. In some examples, a base station ordevice such as one of the base stations 105 or 205 or one of the devices4305, 4405, or 4505 may execute one or more sets of codes to control thefunctional elements of the device to perform the functions describedbelow.

The blocks 4605, 4610, and 4615 illustrated in FIG. 46 provide anexample set of operations to be performed in a plurality of recursiveiterations to synchronize a frequency of at least a first base stationin a network (which in some cases may be a network having properties ofone or more of the networks described with reference to FIGS. 37-42.

At block 4605, frequency information may be received from at least oneneighboring base station of the network. In some cases, the frequencyinformation may be received from the at least one neighboring basestation of the network during a periodic CET, such as one of the CETsdescribed with reference to FIG. 7, 8, 9, 10, 13, 14, 15, 16, 17, 18,22, 23, 24, 25, 26, 27, 29, 30, 31, or 32. In other cases, the frequencyinformation may be received from the at least one neighboring basestation of the network during a periodic frame associated with timesynchronization, such as one of the CCAs described with reference toFIG. 11, 12, 13, 19, 20, 21, 28, 34, 35, or 36.

The operation(s) at block 4605 may be performed by the frequencymanagement module 4315, 4415, or 4515 described with reference to FIG.43, 44, or 45, or the frequency information analysis module 4425 or 4525described with reference to FIG. 44 or 45.

At block 4610, a plurality of coefficient multipliers including aseparate coefficient multiplier for the first base station and each ofthe at least one neighboring base station are generated. The coefficientmultipliers may be based at least in part on a quantity of the at leastone neighboring base station. The plurality of coefficient multipliersmay define a stochastic matrix. The operation(s) at block 4610 may beperformed by the frequency management module 4315, 4415, or 4515described with reference to FIG. 43, 44, or 45, or the coefficientmultiplier generation module 4430 or 4540 described with reference toFIG. 44 or 45.

At block 4615, the frequency of the first base station may be adjustedbased on the received frequency information and the coefficientmultipliers. The operation(s) at block 4615 may be performed by thefrequency management module 4315, 4415, or 4515 described with referenceto FIG. 43, 44, or 45, or the frequency adjustment module 4435 or 4545described with reference to FIG. 44 or 45.

In some examples, the coefficient multipliers may be held constant for aplurality (i.e., two or more) of the recursive iterations through blocks4605, 4610, and 4615. Holding the coefficient multipliers throughmultiple iterations can increase the stability of frequency adjustmentsand frequency convergence (e.g., frequency convergence among multiplebase stations).

Thus, the method 4600 may provide for wireless communication. It shouldbe noted that the method 4600 is just one implementation and that theoperations of the method 4600 may be rearranged or otherwise modifiedsuch that other implementations are possible.

FIG. 47 is a flow chart illustrating an example of a method 4700 ofwireless communication in a network including a plurality of basestations configured to communicate data over an unlicensed spectrum, inaccordance with various aspects of the present disclosure. For clarity,the method4700 is described below with reference to aspects of one ormore of the base stations 105 or 205 described with reference to FIG. 1,2A, or 2B, or one of the devices 4305, 4405, or 4505 described withreference to FIG. 43, 44, or 45. In some examples, a base station ordevice such as one of the base stations 105 or 205 or one of the devices4305, 4405, or 4505 may execute one or more sets of codes to control thefunctional elements of the device to perform the functions describedbelow.

The blocks 4705, 4710, 4715, 4720, and 4725 illustrated in FIG. 47provide an example set of operations to be performed in a plurality ofrecursive iterations to synchronize a frequency of at least a first basestation in a network (which in some cases may be a network havingproperties of one or more of the networks described with reference toFIGS. 37-42.

At block 4705, frequency information may be received from at least oneneighboring base station of the network. In some cases, the frequencyinformation may be received from the at least one neighboring basestation of the network during a periodic CET, such as one of the CETsdescribed with reference to FIG. 7, 8, 9, 10, 13, 14, 15, 16, 17, 18,22, 23, 24, 25, 26, 27, 29, 30, 31, or 32. In other cases, the frequencyinformation may be received from the at least one neighboring basestation of the network during a periodic frame associated with timesynchronization, such as one of the CCAs described with reference toFIG. 11, 12, 13, 19, 20, 21, 28, 34, 35, or 36.

The operation(s) at block 4705 may be performed by the frequencymanagement module 4315, 4415, or 4515 described with reference to FIG.43, 44, or 45, or the frequency information analysis module 4425 or 4525described with reference to FIG. 44 or 45.

At block 4710, a timing stratum of each of the at least one neighboringbase stations may be determined. By way of example, the timing stratummay be determined from the received frequency information or frominformation received in one or more messages over the unlicensedspectrum or another spectrum (e.g., an LTE spectrum). The operation(s)at block 4710 may be performed by the frequency management module 4315,4415, or 4515 described with reference to FIG. 43, 44, or 45, or thetiming stratum determination module 4530 described with reference toFIG. 45.

At block 4715, a link quality of each of the at least one neighboringbase stations may be determined. By way of example, the link quality maybe determined from the received frequency information. The operation(s)at block 4715 may be performed by the frequency management module 4315,4415, or 4515 described with reference to FIG. 43, 44, or 45, or thelink quality determination module 4535 described with reference to FIG.45.

At block 4720, a plurality of coefficient multipliers including aseparate coefficient multiplier for the first base station and each ofthe at least one neighboring base station are generated. The coefficientmultipliers may be based at least in part on a quantity of the at leastone neighboring base station. The coefficient multiplier generated foreach of the at least one neighboring base station may be further basedon the timing stratum associated with that neighboring base station(e.g., to give higher weight to a base station associated with a lowerstratum, such as a GPS source (which in some cases may be assigned acoefficient multiplier of one)). The coefficient multiplier generatedfor each of the at least one neighboring base station may be furtherbased on the link quality associated with that neighboring base station(e.g., to give higher weight to better link qualities). The plurality ofcoefficient multipliers may define a stochastic matrix. The operation(s)at block 4720 may be performed by the frequency management module 4315,4415, or 4515 described with reference to FIG. 43, 44, or 45, or thecoefficient multiplier generation module 4430 or 4540 described withreference to FIG. 44 or 45.

At block 4725, the frequency of the first base station may be adjustedbased on the received frequency information and the coefficientmultipliers. The operation(s) at block 4725 may be performed by thefrequency management module 4315, 4415, or 4515 described with referenceto FIG. 43, 44, or 45, or the frequency adjustment module 4435 or 4545described with reference to FIG. 44 or 45.

In some examples, the coefficient multipliers may be held constant for aplurality (i.e., two or more) of the recursive iterations through blocks4705, 4710, 4715, 4720, and 4725. Holding the coefficient multipliersthrough multiple iterations can increase the stability of frequencyadjustments and frequency convergence (e.g., frequency convergence amongmultiple base stations).

Thus, the method 4700 may provide for wireless communication. It shouldbe noted that the method 4700 is just one implementation and that theoperations of the method 4700 may be rearranged or otherwise modifiedsuch that other implementations are possible.

In some cases, one or more aspects of the method 4600 and the method4700 may be combined. One or more aspects of the method 4600 or 4700 mayalso be combined with one or more aspects of the method 2900, 3000,3100, 3200, 3300, 3400, 3500, or 3600 described in FIG. 29, 30, 31, 32,33, 34, 35, or 36.

FIG. 48 shows a block diagram 4800 illustrating a base station 4805configured for wireless communication, in accordance with variousaspects of the present disclosure. In some examples, the base station4805 may be an example of one or more aspects of one of the basestations 105 or 205 described with reference to FIG. 1, 2A, or 2B, orone of the devices 1305, 1405, 1505, 1605, 1705, 1805, 1905, 2005, 2105,4305, 4405, or 4505 described with reference to FIG. 13, 14, 15, 16, 17,18, 19, 20, 21, 43, 44, or 45. The base station 4805 may be configuredto implement at least some of the features and functions describedherein relating to timing adjustments, frequency adjustments, orwireless communication. The base station 4805 may include a processormodule 4810, a memory module 4820, at least one transceiver module(represented by transceiver module(s) 4855), at least one antenna(represented by antenna(s) 4860), and a shared RF spectrum module 4870.The base station 4805 may also include one or more of a base stationcommunications module 4830, a network communications module 4840, and asystem communications management module 4850. Each of these componentsmay be in communication with each other, directly or indirectly, overone or more buses 4835.

The memory module 4820 may include random access memory (RAM) orread-only memory (ROM). The memory module 4820 may storecomputer-readable, computer-executable software (SW) code 4825containing instructions that are configured to, when executed, cause theprocessor module 4810 to perform various functions described herein forcommunicating over a first radio frequency spectrum (e.g., an LTE/LTE-Aor licensed radio frequency spectrum) or a second radio frequencyspectrum (e.g., a “shared spectrum” such as an unlicensed radiofrequency spectrum), and for transmitting and receiving timing orfrequency information and making timing or frequency adjustments forwireless communication over the second radio frequency spectrum.Alternatively, the software code 4825 may not be directly executable bythe processor module 4810 but be configured to cause the base station4805 (e.g., when compiled and executed) to perform various of thefunctions described herein.

The processor module 4810 may include an intelligent hardware device,e.g., a central processing unit (CPU), a microcontroller, an ASIC, etc.The processor module 4810 may process information received through thetransceiver module(s) 4855, the base station communications module 4830,or the network communications module 4840. The processor module 4810 mayalso process information to be sent to the transceiver module(s) 4855for transmission through the antenna(s) 4860, to the base stationcommunications module 4830 for transmission to one or more other basestations 4805-a and 4805-b (e.g., eNBs), or to the networkcommunications module 4840 for transmission to a core network 4845,which may be an example of aspects of the core network 130 describedwith reference to FIG. 1. The processor module 4810 may handle, alone orin connection with the shared RF spectrum module 4870, various aspectsof communicating over the first radio frequency spectrum or the secondradio frequency spectrum, including aspects of transmitting andreceiving timing or frequency information and making timing or frequencyadjustments for wireless communication over the second radio frequencyspectrum.

The transceiver module(s) 4855 may include a modem configured tomodulate packets and provide the modulated packets to the antenna(s)4860 for transmission, and to demodulate packets received from theantenna(s) 4860. The transceiver module(s) 4855 may in some cases beimplemented as one or more transmitter modules and one or more separatereceiver modules. The transceiver module(s) 4855 may supportcommunications in the first radio frequency spectrum or the second radiofrequency spectrum. The transceiver module(s) 4855 may be configured tocommunicate bi-directionally, via the antenna(s) 4860, with one or moreof the UEs 115 or 215 described with reference to FIG. 1, 2A, or 2B, forexample. The base station 4805 may typically include multiple antennas4860 (e.g., an antenna array). The base station 4805 may communicatewith the core network 4845 through the network communications module4840. The base station 4805 may also communicate with other basestations, such as the base stations 4805-a and 4805-b, using the basestation communications module 4830. In some cases, the base station 4805may communicate with the other base stations 4805-a and 4805-b for thepurpose of exchanging timing or frequency information and making timingor frequency adjustments for wireless communication over the secondradio frequency spectrum.

According to the architecture of FIG. 48, the system communicationsmanagement module 4850 may manage communications with other basestations, eNBs, or devices. In some cases, functionality of the systemcommunications management module 4850 may be implemented as a componentof the transceiver module(s) 4855, as a computer program product, or asone or more controller elements of the processor module 4810.

The shared RF spectrum module 4870 may be configured to perform orcontrol some or all of the features or functions described withreference to any or all of FIGS. 1, 2A, 2B, and 3-47 related to wirelesscommunication in a first radio frequency spectrum or a second radiofrequency spectrum, including the exchange of timing or frequencyinformation and the making of timing or frequency adjustments forwireless communication over the second radio frequency spectrum. In somecases, the shared RF spectrum module 4870 may be configured to support asupplemental downlink mode, a carrier aggregation mode, or a standalonemode of operation in the second radio frequency spectrum. The shared RFspectrum module 4870 may include an LTE module 4875 configured to handleLTE/LTE-A communications in licensed spectrum, an LTE unlicensed module4880 configured to handle

LTE/LTE-A communications in unlicensed spectrum, or an unlicensed module4885 configured to handle communications other than LTE/LTE-A in anunlicensed spectrum. The shared RF spectrum module 4870 may also includea timing and frequency management module 4890. The timing and frequencymanagement module 4890 may be an example of one or more aspects of thetiming management module 1315, 1415, 1515, 1615, 1715, 1815, 1915, 2015,or 2115 described with reference to FIG. 13, 14, 15, 16, 17, 18, 19, 20,or 21, or the frequency management module 4315, 4415, or 4515 describedwith reference to FIG. 43, 44, or 45. The shared RF spectrum module4870, or portions of it, may include a processor, or some or all of thefunctionality of the shared RF spectrum module 4870 may be performed bythe processor module 4810 or in connection with the processor module4810.

The detailed description set forth above in connection with the appendeddrawings describes exemplary embodiments and does not represent the onlyexamples that may be implemented or that are within the scope of theclaims. The terms “example” and “exemplary,” when used in thisdescription, mean “serving as an example, instance, or illustration,”and not “preferred” or “advantageous over other examples.” The detaileddescription includes specific details for the purpose of providing anunderstanding of the described techniques. These techniques, however,may be practiced without these specific details. In some instances,well-known structures and devices are shown in block diagram form inorder to avoid obscuring the concepts of the described examples.

Information and signals may be represented using any of a variety ofdifferent technologies and techniques. For example, data, instructions,commands, information, signals, bits, symbols, and chips that may bereferenced throughout the above description may be represented byvoltages, currents, electromagnetic waves, magnetic fields or particles,optical fields or particles, or any combination thereof

The various illustrative blocks and modules described in connection withthe disclosure herein may be implemented or performed with ageneral-purpose processor, a digital signal processor (DSP), an ASIC, anFPGA or other programmable logic device, discrete gate or transistorlogic, discrete hardware components, or any combination thereof designedto perform the functions described herein. A general-purpose processormay be a microprocessor, but in the alternative, the processor may beany conventional processor, controller, microcontroller, or statemachine. A processor may also be implemented as a combination ofcomputing devices, e.g., a combination of a DSP and a microprocessor,multiple microprocessors, one or more microprocessors in conjunctionwith a DSP core, or any other such configuration.

The functions described herein may be implemented in hardware, softwareexecuted by a processor, firmware, or any combination thereof. Ifimplemented in software executed by a processor, the functions may bestored on or transmitted over as one or more instructions or code on acomputer-readable medium. Other examples and implementations are withinthe scope and spirit of the disclosure and appended claims. For example,due to the nature of software, functions described above can beimplemented using software executed by a processor, hardware, firmware,hardwiring, or combinations of any of these. Features implementingfunctions may also be physically located at various positions, includingbeing distributed such that portions of functions are implemented atdifferent physical locations. Also, as used herein, including in theclaims, “or” as used in a list of items prefaced by “at least one of”indicates a disjunctive list such that, for example, a list of “at leastone of A, B, or C” means A or B or C or AB or AC or BC or ABC (i.e., Aand B and C).

Computer-readable media includes both computer storage media andcommunication media including any medium that facilitates transfer of acomputer program from one place to another. A storage medium may be anyavailable medium that can be accessed by a general purpose or specialpurpose computer. By way of example, and not limitation,computer-readable media can comprise RAM, ROM, EEPROM, CD-ROM or otheroptical disk storage, magnetic disk storage or other magnetic storagedevices, or any other medium that can be used to carry or store desiredprogram code means in the form of instructions or data structures andthat can be accessed by a general-purpose or special-purpose computer,or a general-purpose or special-purpose processor. Also, any connectionis properly termed a computer-readable medium. For example, if thesoftware is transmitted from a website, server, or other remote sourceusing a coaxial cable, fiber optic cable, twisted pair, digitalsubscriber line (DSL), or wireless technologies such as infrared, radio,and microwave, then the coaxial cable, fiber optic cable, twisted pair,DSL, or wireless technologies such as infrared, radio, and microwave areincluded in the definition of medium. Disk and disc, as used herein,include compact disc (CD), laser disc, optical disc, digital versatiledisc (DVD), floppy disk and Blu-ray disc where disks usually reproducedata magnetically, while discs reproduce data optically with lasers.Combinations of the above are also included within the scope ofcomputer-readable media.

The previous description of the disclosure is provided to enable aperson skilled in the art to make or use the disclosure. Variousmodifications to the disclosure will be readily apparent to thoseskilled in the art, and the generic principles defined herein may beapplied to other variations without departing from the spirit or scopeof the disclosure. Throughout this disclosure the term “example” or“exemplary” indicates an example or instance and does not imply orrequire any preference for the noted example. Thus, the disclosure isnot to be limited to the examples and designs described herein but is tobe accorded the widest scope consistent with the principles and novelfeatures disclosed herein.

What is claimed is:
 1. A method of wireless communication, comprising:identifying a clear channel assessment (CCA) slot assigned to a firstbase station for a frame of a shared spectrum, the frame associated withtime synchronization; performing a CCA at the identified CCA slot forthe frame based on a timing stratum of the CCA slot, the timing stratumindicating a number of hops between the first base station and a globalpositioning service (GPS) synchronized timing source; gating, based onthe timing stratum of the first base station, a CCA frequency of thefirst base station for a plurality of frames associated with timingsynchronization; selectively transmitting a first timing information ofthe first base station during at least one reference signal resourceelement of the frame in response to determining that the CCA issuccessful; and listening for a second timing information of a secondbase station during the frame when the CCA is unsuccessful.
 2. Themethod of claim 1, wherein a periodicity of the gating is based on thetiming stratum of the first base station.
 3. The method of claim 1,further comprising: determining that the CCA is unsuccessful; receiving,at the first base station, a channel usage beacon signal from the secondbase station for the frame.
 4. The method of claim 3, furthercomprising: receiving the second timing information from the second basestation during the frame; and adjusting a timing of the first basestation based on the second timing information received from the secondbase station during the frame.
 5. The method of claim 4, furthercomprising: adjusting the timing of the first base station based on athird timing information received from a third base station.
 6. Themethod of claim 1, further comprising: transmitting data to at least oneuser equipment (UE) during the frame, wherein the data is transmitted tothe UE concurrent with the transmission of the first timing information.7. An apparatus for wireless communication, comprising: a processor; andmemory coupled to the processor, wherein the processor is configured to:identify a clear channel assessment (CCA) slot assigned to a first basestation for a frame of a shared spectrum, the frame associated with timesynchronization; perform a CCA at the identified CCA slot for the framebased on a timing stratum of the CCA slot, the timing stratum indicatinga number of hops between the first base station and a global positioningservice (GPS) synchronized timing source; gate, based on the timingstratum of the first base station, a CCA frequency of the first basestation for a plurality of frames associated with timingsynchronization; selectively transmit a first timing information of thefirst base station during at least one reference signal resource elementof the frame in response to determining that the CCA is successful; andlisten for a second timing information of a second base station duringthe frame when the CCA is unsuccessful.
 8. The apparatus of claim 7,wherein a periodicity of the gating is based on the timing stratum ofthe first base station.
 9. The apparatus of claim 7, wherein theprocessor is further configured to: determine that the CCA isunsuccessful; receive, at the first base station, a channel usage beaconsignal from the second base station for the frame.
 10. The apparatus ofclaim 7, wherein the processor is further configured to: transmit datato at least one user equipment (UE) during the frame, wherein the datais transmitted to the UE concurrent with the transmission of the firsttiming information.
 11. A non-transitory computer-readable mediumstoring computer-executable code for wireless communication, the codeexecutable by a processor to: identify a clear channel assessment (CCA)slot assigned to a first base station for a frame of a shared spectrum,the frame associated with time synchronization; perform a CCA at theidentified CCA slot for the frame based on a timing stratum of the CCAslot, the timing stratum indicating a number of hops between the firstbase station and a global positioning service (GPS) synchronized timingsource; gate, based on the timing stratum of the first base station, aCCA frequency of the first base station for a plurality of framesassociated with timing synchronization; selectively transmit a firsttiming information of the first base station during at least onereference signal resource element of the frame in response todetermining that the CCA is successful; and listen for a second timinginformation of a second base station during the frame when the CCA isunsuccessful.
 12. The non-transitory computer-readable medium of claim11, wherein a periodicity of the gating is based on the timing stratumof the first base station.
 13. The non-transitory computer-readablemedium of claim 11, wherein the instructions are executable by theprocessor to: determine that the CCA is unsuccessful; and receive, atthe first base station, a channel usage beacon signal from the secondbase station for the frame.
 14. The non-transitory computer-readablemedium of claim 13, wherein the instructions are executable by theprocessor to: receive the second timing information from the second basestation during the frame; and adjust a timing of the first base stationbased on the second timing information received from the second basestation during the frame.
 15. The non-transitory computer-readablemedium of claim 14, wherein the instructions are executable by theprocessor to: adjust the timing of the first base station based on athird timing information received from a third base station.
 16. Thenon-transitory computer-readable medium of claim 11, wherein theinstructions are executable by the processor to: transmit data to atleast one user equipment (UE) during the frame, wherein the data istransmitted to the UE concurrent with the transmission of the firsttiming information.
 17. An apparatus for wireless communication,comprising: means for identifying a clear channel assessment (CCA) slotassigned to a first base station for a frame of a shared spectrum, theframe associated with time synchronization; means for performing a CCAat the identified CCA slot for the frame based on a timing stratum ofthe CCA slot, the timing stratum indicating a number of hops between thefirst base station and a global positioning service (GPS) synchronizedtiming source; means for gating, based on the timing stratum of thefirst base station, a CCA frequency of the first base station for aplurality of frames associated with timing synchronization; means forselectively transmitting a first timing information of the first basestation during at least one reference signal resource element of theframe in response to determining that the CCA is successful; and meansfor listening for a second timing information of a second base stationduring the frame when the CCA is unsuccessful.
 18. The apparatus ofclaim 17, wherein a periodicity of the gating is based on the timingstratum of the first base station.
 19. The apparatus of claim 17,further comprising: means for determining that the CCA is unsuccessful;means for receiving, at the first base station, a channel usage beaconsignal from the second base station for the frame.
 20. The apparatus ofclaim 19, further comprising: means for receiving the second timinginformation from the second base station during the frame; and means foradjusting a timing of the first base station based on the second timinginformation received from the second base station during the frame. 21.The apparatus of claim 20, further comprising: means for adjusting thetiming of the first base station based on a third timing informationreceived from a third base station.
 22. The apparatus of claim 17,further comprising: means for transmitting data to at least one userequipment (UE) during the frame, wherein the data is transmitted to theUE concurrent with the transmission of the first timing information.